OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..55
Eric Weisstein's World of Mathematics, Partition
Eric Weisstein's World of Mathematics, Partition Function P
MAPLE
with(numtheory): P:= proc(n) local d, j; P(n):= `if`(n=0, 1, add(add(d, d=divisors(j)) *P(n-j), j=1..n)/n) end: b:= proc(n, i) if n<0 then 0 elif n=0 then 1 elif i=0 then 0 else b(n, i):= b(n, i-1) +b(n-i, i) fi end: a:= n-> b(P(n), n): seq(a(n), n=1..25); # Alois P. Heinz, Jul 17 2009
MATHEMATICA
(* first do *) Needs["DiscreteMath`IntegerPartitions`"] (* then *) a[n_] := Length@ IntegerPartitions[ PartitionsP[n], n] (* Robert G. Wilson v, Nov 11 2007 *)
P[n_] := P[n] = Module[{d, j}, If[n == 0, 1, Sum[DivisorSum[j, #&]*P[n - j], {j, 1, n}]/n]]; b [n_, i_] := b[n, i] = Which[n<0, 0, n == 0, 1, i == 0, 0, True, b[n, i] = b[n, i-1] + b[n-i, i]]; a[n_] := b[P[n], n]; Table [a[n], {n, 1, 25}] (* Jean-François Alcover, Nov 11 2015, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 07 2007
EXTENSIONS
More terms from Alois P. Heinz, Jul 17 2009
STATUS
approved