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.

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A294250 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f.: exp(Product_{j=1..n} (1+x^j) - 1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 3, 1, 0, 1, 1, 3, 13, 1, 0, 1, 1, 3, 19, 49, 1, 0, 1, 1, 3, 19, 97, 261, 1, 0, 1, 1, 3, 19, 121, 681, 1531, 1, 0, 1, 1, 3, 19, 121, 921, 5971, 9073, 1, 0, 1, 1, 3, 19, 121, 1041, 8491, 50443, 63393, 1, 0, 1, 1, 3, 19, 121, 1041
Offset: 0

Views

Author

Seiichi Manyama, Oct 26 2017

Keywords

Examples

			Square array A(n,k) begins:
   1, 1,   1,   1,   1, ...
   0, 1,   1,   1,   1, ...
   0, 1,   3,   3,   3, ...
   0, 1,  13,  19,  19, ...
   0, 1,  49,  97, 121, ...
   0, 1, 261, 681, 921, ...
		

Crossrefs

Columns k=0..5 give A000007, A000012, A118589, A294251, A294252, A294253.
Rows n=0 gives A000012.
Main diagonal gives A293840.

Formula

B(j,k) is the coefficient of Product_{i=1..k} (1+x^i).
A(0,k) = 1 and A(n,k) = (n-1)! * Sum_{j=1..min(A000217(k),n)} j*B(j,k)*A(n-j,k)/(n-j)! for n > 0.

A327674 Number of colored compositions of n using all colors of an n-set such that the color patterns for parts i are sorted and have i (distinct) colors (in arbitrary order).

Original entry on oeis.org

1, 1, 3, 19, 121, 1041, 11191, 130663, 1731969, 25778161, 432791371, 7752723771, 151553121193, 3178030999729, 71244609480591, 1716351868658911, 43661944977384961, 1173984102030774753, 33302371396771085779, 991402105480284394531, 30912472614894951462681
Offset: 0

Views

Author

Alois P. Heinz, Sep 21 2019

Keywords

Comments

Differs from A293840 and from A294253 first at n = 6.

Examples

			a(3) = 19: 3abc, 3acb, 3bac, 3bca, 3cab, 3cba, 2ab1c, 2ac1b, 2ba1c, 2bc1a, 2ca1b, 2cb1a, 1a2bc, 1a2cb, 1b2ac, 1b2ca, 1c2ab, 1c2ba, 1a1b1c.
		

Crossrefs

Main diagonal of A327673.

Programs

  • Maple
    b:= proc(n, i, k, p) option remember;
         `if`(n=0, p!, `if`(i<1, 0, add(binomial(k^i, j)*
          b(n-i*j, min(n-i*j, i-1), k, p+j)/j!, j=0..n/i)))
        end:
    a:= n-> add(b(n$2, i, 0)*(-1)^(n-i)*binomial(n, i), i=0..n):
    seq(a(n), n=0..21);
  • Mathematica
    b[n_, i_, k_, p_] := b[n, i, k, p] =
         If[n == 0, p!, If[i < 1, 0, Sum[Binomial[k^i, j]*
         b[n - i j, Min[n - i j, i - 1], k, p + j]/j!, {j, 0, n/i}]]];
    a[n_] := Sum[b[n, n, i, 0] (-1)^(n-i) Binomial[n, i], {i, 0, n}];
    Table[a[n], {n, 0, 21}] (* Jean-François Alcover, Aug 01 2021, after Alois P. Heinz *)

Formula

a(n) = A327673(n,n).
Showing 1-2 of 2 results.