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.

A198889 Square array in A071223 read by antidiagonals.

Original entry on oeis.org

2, 2, 2, 2, 6, 2, 2, 12, 6, 2, 2, 20, 24, 6, 2, 2, 30, 72, 24, 6, 2, 2, 42, 172, 120, 24, 6, 2, 2, 56, 352, 480, 120, 24, 6, 2, 2, 72, 646, 1512, 720, 120, 24, 6, 2, 2, 90, 1094, 3976, 3600, 720, 120, 24, 6, 2, 2, 110, 1742, 9144, 14184, 5040, 720, 120, 24, 6, 2, 2, 132, 2642, 18990, 45992, 30240, 5040, 720, 120
Offset: 2

Views

Author

N. J. A. Sloane, Oct 30 2011

Keywords

Examples

			Array begins
  2  2   2   2   2  ...
  2  6   6   6   6 ...
  2 12  24  24  24 ...
  2 20  72 120 120 ...
  2 30 172 480 720 ...
  ...
		

Crossrefs

Cf. A071223.

Programs

  • Maple
    A071223 := proc(n,k)
            if k=1 and n>=2 then
                    2
            elif n=2 and k>=1 then
                    2
            elif k>=n-1 then
                    n!
            else
            procname(n-1, k)+(n-1)*procname(n-1, k-1)
            fi ;
    end proc:
    for d from 3 to 16 do
            for k from 1 to d-2 do
                    n := d-k ;
                    printf("%d,",A071223(n,k)) ;
            end do:
    end do; # R. J. Mathar, Oct 31 2011

Formula

See A071223, which is the main entry for this array.