OFFSET
1,4
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
a(1) = 1; a(n > 1) = Sum_{d = 1..n-1} a(d) * floor((n-1)/d - 1).
G.f. A(x) satisfies A(x) = x + (x/(1 - x)) * Sum_{k>=2} A(x^k). - Ilya Gutkovskiy, Sep 06 2019
MATHEMATICA
sau[n_]:=If[n==1, 1, Sum[sau[d], {k, n-1}, {d, Most[Divisors[k]]}]];
Table[sau[n], {n, 60}]
PROG
(Magma) sol:=[1]; for n in [2..56] do Append(~sol, &+[sol[d]*Floor((n-1)/d-1):d in [1..n-1]]); end for; sol; // Marius A. Burtea, Sep 07 2019
(PARI) seq(n)={my(v=vector(n)); v[1]=1; for(n=2, #v, v[n]=sum(k=1, n-1, v[k]*((n-1)\k - 1))); v} \\ Andrew Howroyd, Sep 07 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 07 2018
STATUS
approved