A306009 Inverse Weigh transform of A000085.

1, 2, 2, 7, 14, 43, 130, 446, 1544, 5773, 22170, 89356, 370198, 1591379, 7020014, 31922981, 148679262, 710828036, 3474337098, 17379964444, 88739068866, 462670294023, 2458638559154, 13317850411827, 73432568553848, 412120738922369, 2351720323257872

Offset: 1

Author

Alois P. Heinz, Jun 16 2018

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..800

Crossrefs

Cf. A000085, A293114.

Programs

Maple

g:= proc(n) option remember;
      `if`(n<2, 1, g(n-1)+(n-1)*g(n-2))
    end:
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
      add(binomial(a(i), j)*b(n-i*j, i-1), j=0..n/i)))
    end:
a:= proc(n) option remember; g(n)-b(n, n-1) end:
seq(a(n), n=1..30);

Mathematica

g[n_] := g[n] = If[n < 2, 1, g[n - 1] + (n - 1)*g[n - 2]];
b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, Sum[Binomial[a[i], j]*b[n - i*j, i - 1], {j, 0, n/i}]]];
a[n_] := a[n] = g[n] - b[n, n - 1];
Table[a[n], {n, 1, 30}] (* Jean-François Alcover, Oct 27 2021, after Alois P. Heinz *)

Formula

Product_{k>=1} (1+x^k)^a(k) = Sum_{n>=0} A000085(n) * x^n.