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.

A327847 Number of colored compositions of n using all colors of a 2-set such that all parts have different color patterns and the patterns for parts i have i colors in (weakly) increasing order.

Original entry on oeis.org

0, 0, 3, 10, 39, 100, 303, 782, 2009, 5388, 12839, 32658, 79673, 191500, 459745, 1090622, 2569597, 5932304, 13906405, 31740090, 72160311, 164296384, 369673125, 827781598, 1834885695, 4076433368, 8966677703, 19639987986, 42751905899, 92703023676, 200647122467
Offset: 0

Views

Author

Alois P. Heinz, Sep 27 2019

Keywords

Examples

			a(3) = 10: 3aab, 3abb, 2aa1b, 2ab1a, 2ab1b, 2bb1a, 1a2ab, 1a2bb, 1b2aa, 1b2ab.
		

Crossrefs

Column k=2 of A327245.

Programs

  • Maple
    b:= proc(n, i, k, p) option remember; `if`(n=0, p!,
         `if`(i<1, 0, add(b(n-i*j, min(n-i*j, i-1), k, p+j)*
          binomial(binomial(k+i-1, i), j), j=0..n/i)))
        end:
    a:= n-> (k-> add(b(n$2, i, 0)*(-1)^(k-i)*binomial(k, i), i=0..k))(2):
    seq(a(n), n=0..37);