cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A219356 Triangle read by rows: A219274 with rows reversed.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 1, 4, 5, 1, 5, 9, 16, 1, 6, 14, 49, 1, 7, 20, 92, 70, 1, 8, 27, 153, 204, 168, 1, 9, 35, 235, 405, 738, 768, 1, 10, 44, 341, 715, 1815, 3300, 1, 11, 54, 474, 1166, 3630, 9460, 7887, 1, 12, 65, 637, 1794, 6578, 21307, 28743, 15015
Offset: 0

Views

Author

Alois P. Heinz, Nov 18 2012

Keywords

Comments

For more information see A219274.

Examples

			A219274 with rows reversed begins:
  1;
  1;
  1;
  1,  2;
  1,  3;
  1,  4,  5;
  1,  5,  9,  16;
  1,  6, 14,  49;
  1,  7, 20,  92,  70;
  1,  8, 27, 153, 204, 168;
  1,  9, 35, 235, 405, 738, 768;
  ...
		

Crossrefs

Row lengths are A122797 (for n>0).
Row sums give: A218293.
Last elements of rows give: A219339.

Programs

  • Maple
    h:= proc(l) local n; n:=nops(l); add(i, i=l)!/mul(mul(1+l[i]-j+
          add(`if`(l[k]>=j, 1, 0), k=i+1..n), j=1..l[i]), i=1..n)
        end:
    g:= proc(n, i, l) local s; s:=i*(i+1)/2;
          `if`(n=s, h([l[], seq(i-j, j=0..i-1)]), `if`(n>s, 0,
           g(n, i-1, l)+ `if`(i>n, 0, g(n-i, i-1, [l[], i]))))
        end:
    T:= (n, k)-> `if`(k>n, 0, g(n-k, k-1, [k])):
    seq(seq(T(n, n-k), k=0..(n-floor(sqrt(2*n)+1/2))), n=0..14);