OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..604
FORMULA
E.g.f.: exp(x+x^2/2+x^4/4!+x^8/8!+x^16/16!+...).
MAPLE
with(combinat):
b:= proc(n, i) option remember; `if`(n=0, 1,
`if`(i<1, 0, add(multinomial(n, n-i*j, i$j)/j!*
b(n-i*j, i/2), j=0..n/i)))
end:
a:= n-> b(n, 2^ilog2(n)):
seq(a(n), n=0..30); # Alois P. Heinz, Sep 17 2015
# second Maple program:
a:= proc(n) option remember; `if`(n=0, 1, add((j->
a(n-j)*binomial(n-1, j-1))(2^i), i=0..ilog2(n)))
end:
seq(a(n), n=0..30); # Alois P. Heinz, Apr 21 2023
MATHEMATICA
multinomial[n_, k_List] := n!/Times @@ (k!); b[n_, i_] := b[n, i] = If[n == 0, 1, If[i<1, 0, Sum[multinomial[n, Join[{n-i*j}, Array[i&, j]]]/j!*b[n - i*j, i/2], {j, 0, n/i}]]]; a[n_] := b[n, 2^Floor[Log[2, n]]]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Oct 29 2015, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Christian G. Bower, Jan 26 2006
STATUS
approved