A100034 Bisection of A000081 (even part).

0, 1, 4, 20, 115, 719, 4766, 32973, 235381, 1721159, 12826228, 97055181, 743724984, 5759636510, 45007066269, 354426847597, 2809934352700, 22409533673568, 179655930440464, 1447023384581029, 11703780079612453, 95020085893954917, 774088023431472074

Offset: 0

Author

N. J. A. Sloane, Nov 20 2004

Keywords

• nonn
• easy

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..400

Crossrefs

Cf. A000081, A100427, A299098.

Programs

Maple

with(numtheory):
b:= proc(n) option remember; local d, j; `if`(n<2, n,
      (add(add(d*b(d), d=divisors(j))*b(n-j), j=1..n-1))/(n-1))
    end:
a:= n-> b(2*n):
seq(a(n), n=0..50);  # Alois P. Heinz, May 16 2013

Mathematica

b[n_] := b[n] = If[n <= 1, n, Sum[Sum[d*b[d], {d, Divisors[j]}]*b[n-j], {j, 1, n-1}]/(n-1)]; a[n_] := b[2*n]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Mar 19 2014, after Alois P. Heinz *)

Extensions

More terms from Joshua Zucker, May 12 2006