Talk:Pascal's pyramid

Why is this called a pyramid? The base is a triangle, so isn't it a tetrahedron?

A tetrahedron is a pyramid. Factitious 00:47, Jun 25, 2005 (UTC)

@Factitious: A tetrahedron is a type or pyramid. And actually it is known as Pascal's triangle, hence I have suggested a merge. ^∞😃 Target360YT 😃^∞ (talk · contribs) 06:03, 10 October 2016 (UTC)[reply]

> Summing the numbers in each column of a layer of Pascal's pyramid gives the nth power of 111 in base infinity (i.e. without carrying over during multiplication), where n is the layer - 1.

Is it really accurate to call this "base infinity"? It's more accurately base 10 (but without said carry-over). Actually, more generally, it's the nth power of 111 in any base. For example, in base 9, 111^2 = 12321:
1 + 2*9 + 3*9^2 + 2*9^3 + 1*9^4 = 8281 = (1 + 9 + 81)^2. --Matthew0028 13:53, 14 February 2006 (UTC)[reply]

Yes, base 9 works for 111^2, however as you get into higher powers of 111, you are forced, according to the rules of multiplication, to carry over. Higher number bases allow for higher nmbers to not be carried over. Base "infinity" makes the rule applicable to all powers of 111. I take the blame for making up the term "base infinity", however in this situation I feel that it is quite a good description of what is actually happening.

What is actually happening is a degeneration, a summing of digits of partial results of the power. You can easily avoid this, even without the "base infinity", just insert some zeroes:

                  1                              1
                 40                            400
               1000                         100000
              16000                       16000000
             190000                     1900000000
            1600000                   160000000000
           10000000                 10000000000000
           40000000                400000000000000
          100000000              10000000000000000
          ---------              -----------------
  111^4 = 151807041    10101^4 = 10410161916100401, or 1 04 10 16 19 16 10 04 01

which is the layer columns sum you were looking for. But again, this is just another degeneration of the original layer itself. Let's insert some more zeroes:

  10000000101^4 = 10000000404000006120600041212040104060401, or
                  1
     00 00 00 04 04
     00 00 06 12 06
     00 04 12 12 04
     01 04 06 04 01

and you get the original layer itself. There's a formula for inserting the zeroes in Pascal's simplex.

(endless.oblivion (talk) 00:24, 4 April 2010 (UTC))[reply]

Dead Link?[edit]

http://people.ucsc.edu/~erowland/pascal.html : Not Found The requested URL /~erowland/pascal.html was not found on this server. --NeoUrfahraner 10:00, 15 November 2006 (UTC)[reply]

Multiplication Fact 154.181.255.152 (talk) 12:02, 28 September 2022 (UTC)[reply]

the numbers in Pascal's pyramid can be found by summing the three numbers in the preceding layer. The same as you can find the numbers of pascal's triangle by summing the two numbers in the preceding row.

Major rewrite[edit]

Time waits for no man. I started to extend and clarify this page last June, when I was routed to the hospital to have some of my lung removed. I'm back, but I see someone has a different idea of how the article should flow and has rearranged my order. So I thought I would preview how I think the article should proceed.

I am aiming the text at a target audience that has some familiarity with Pascal's Triangle, but is not a "numbers nut" like me. By showing readers the natural source of the numbers, they should come to appreciate their significance and develop an understanding of the most intuitive and simplest ways to generate the numbers. My focus is on how the Tetrahedron fits into the real world (probability theory and algebra), rather than cleaver ways the numbers can be generated and manipulated. The Tetrahedron is not a stand-alone structure, but part of the continuum of mathematics, in which everything is related to everything else.

Here are the sections as I see them. Not seeing any objections, I will continue as planned.

General introduction (as is)

Table of contents

Structure of the Tetrahedron (existing tables of layers (0 to 5); [currently "Construction"])

Overview of the Tetrahedron (brief preview of the following sections; [currently "Features"])

Trinomial expansion connection (use (A+B+C)^4 as example to show expansion coefficients same as numbers of Tetrahedron; [NEW])

Trinomial distribution connection (relationship of expansion exponents to distribution coefficients--algebraic form [NEW] and combinatorial form [currently "Trinomial construction"])

Parallels with Pascal's Triangle and Multinomial Coefficients ([NEW]; table of 3 columns and several rows:

Type of polynomial [bi-, tri-, multi-nomial]

Order of polynomial [2, 3, m]

Example of polynomial [A+B, A+B+C, A+B+C...+M]

Geometric structure [triangle, pyramid, clusters]

Element structure [line, layer, group]

Symmetry of element [2-way, 3-way, m-way]

Number of terms per element [n+1, (n+1) (n+2)/2, (n+1) (n+2) ... (n+m-1)/(m-1)

Sum of exponents, all terms [n, n, n]

Sum of values per element [2^n, 3^n, m^n]

Coefficient equation [n!/(x! y!), n!/(x! y! z!), n!/(x1! x2! x3! ...xm!)

Sum of numbers "above" [2, 3, m]

Ratio of ad--Colin.campbell.27 (talk) 05:55, 9 January 2011 (UTC)jacent numbers [2, 6, (m) (m-1)][reply]

Sum of adjacent terms in prior layer ([currently "Sum of numbers in layer above"]; better illustration with numbers replacing red and black dots)

Ratio of adjacent terms in same layer ([NEW]; ratios related to expansion exponents; example using (A+B+C)^4):

Other Relationships (which need further discussion when we get there)

“Exponentiational” construction

Sum of coefficients of a layer by rows

Sum of coefficients of a layer by columns

--Colin.campbell.27 (talk) 05:55, 9 January 2011 (UTC)[reply]

Colin, although I appreciate your time investment into this article, I feel the urge to point out a few things:

who do you think the real target audience is? a 4th-grader? well, it may be, but if s/he finds it too hard to understand, the s/he should try to undestand the prerequisites first; for anyone skilled enough to understand polynomial expansion, this level of detailed explanation is almost offending
you talk about "the continuum of mathematics", then you should wikify the text not just to prove it, but to ease the search for knowledge prerequisites even for the 4th-grader, that would allow you to make the text more condensed by avoiding explanations already done elsewhere
there is a discussion at wiki guidelines about the correct form of mathematic articles, mainly if the proof belongs to such an article at all; the content of wikipaedia in general, should be encyclopaedic, dense, not extensively descriptive, like in a book, not a how-to guide, there are separate sections for these: wiki books, wiki how-tos
you may be a skilled educational book writer, but this is not a book, an average reader will not read the article all-through, because usually s/he's just looking for something particular, so you should strive to make the text more modular, and more "sexy" (more images, nicer formulae, etc.), so s/he can find that particular section quickly (e.g., I've seen a nice picture on neighbouring element ratios, that you've done in text here)
see Multinomial theorem or Stirling numbers of the second kind for examples of mudularization and neat formulae; try to talk in math symbols instead of descriptive words
when you get to the last sections (Exponential construction), which I am the author of, let me know, I'm open for discussion; the Sums sections are just improvements of somebody's previous work and I don't regard them as substantial, it's just a number play and I can't see any real use, but you never know, somebody can find it useful...

To sum it up, now I find the article really hard to read, to go through, to find there anything... well, it may be just me.

endless.oblivion (talk) 09:48, 26 February 2011 (UTC)[reply]

Bug in expression?[edit]

In the section Relationship with Pascal's Triangle, there seems to be a bug in the formula C(i,j) × C(n,j) = C(n,i,j), I think it should be C(i,j) × C(n,i) = C(n,i,j) — Preceding unsigned comment added by 88.174.64.89 (talk) 09:26, 1 October 2011 (UTC)[reply]

Requested move 16 August 2023[edit]

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: Not moved. (non-admin closure) SnowFire (talk) 15:23, 25 August 2023 (UTC)[reply]

Pascal's pyramid → Pascal's tetrahedron – When we hear the word "pyramid" we latch onto square pyramids more easily. Thus, Pascal's tetrahedron means what this article is about (A046816) and Pascal's pyramid can equally mean A086754. Georgia guy (talk) 23:39, 16 August 2023 (UTC)[reply]

Oppose – The current title is much more common in books. Dicklyon (talk) 05:32, 17 August 2023 (UTC)[reply]
Oppose per WP:COMMONNAME. I see the same results as Dicklyon in Google Scholar title searches: 21 for "Pascal's pyramid", only 2 for "Pascal's tetrahedron". Spot-checking suggests that most or all of these are on the same topic. —David Eppstein (talk) 17:45, 17 August 2023 (UTC)[reply]

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.