A363453 Total number of blocks containing only even elements in all partitions of [n].

0, 0, 1, 2, 12, 35, 206, 780, 4949, 22686, 156972, 837333, 6301550, 38122554, 310279615, 2090641920, 18293310174, 135445359397, 1267153412532, 10202944645270, 101557600812015, 881921432827544, 9299499328238110, 86508104545175503, 962663031508255416

Offset

0,4

Links

Alois P. Heinz, Table of n, a(n) for n = 0..250

Wikipedia, Partition of a set

Formula

a(n) = Sum_{k=0..floor(n/2)} k * A124422(n,k).

a(n) = A363434(n) - A363452(n).

a(2n) = A363452(2n).

a(2n+1) = A363452(2n+1) - A094577(n).

Example

a(3) = 2 = 0 + 0 + 1 + 0 + 1 : 123, 12|3, 13|2, 1|23, 1|2|3.

Maple

b:= proc(n, k) local g, u; g:= floor(n/2); u:=ceil(n/2);
      add(Stirling2(i, k)*binomial(g, i)*
      add(Stirling2(u, j)*j^(g-i), j=0..u), i=k..g)
    end:
a:= n-> add(b(n, k)*k, k=0..floor(n/2)):
seq(a(n), n=0..25);
# second Maple program:
b:= proc(n, x, y, m) option remember; `if`(n=0, x,
      `if`(x+m>0, b(n-1, y, x, m)*(x+m), 0)+b(n-1, y, x+1, m)+
      `if`(y>0, b(n-1, y-1, x, m+1)*y, 0))
    end:
a:= n-> b(n, 0$3):
seq(a(n), n=0..25);

Mathematica

b[n_, x_, y_, m_] := b[n, x, y, m] = If[n == 0, x,
    If[x+m > 0, b[n-1, y, x, m]*(x+m), 0] + b[n-1, y, x+1, m] +
    If[y > 0, b[n-1, y-1, x, m+1]*y, 0]];
a[n_] := b[n, 0, 0, 0];
Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Dec 08 2023, after Alois P. Heinz *)

Crossrefs

Cf. A000110, A094577, A124422, A363434, A363452.

Sequence in context: A062094 A334838 A200543 * A246426 A353503 A176583

Adjacent sequences: A363450 A363451 A363452 * A363454 A363455 A363456

Keyword

nonn

Author

Alois P. Heinz, Jun 02 2023

Status

approved