OFFSET
1,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..3000
FORMULA
a(n) ~ -(-1)^n * c * 2^n, where c = 0.245410823583396667908354210407104718986708517177206856531763635090205896729... - Vaclav Kotesovec, Sep 09 2019
MATHEMATICA
a[n_] := a[n] = -Sum[a[(n - 1)/d] a[d], {d, Divisors[n - 1]}]; a[1] = 1; Table[a[n], {n, 1, 35}]
PROG
(PARI) seq(n)={my(v=vector(n)); v[1]=1; for(n=1, #v-1, v[n+1] = -sumdiv(n, d, v[d]*v[n/d])); v} \\ Andrew Howroyd, Sep 05 2019
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Sep 05 2019
STATUS
approved