OFFSET
0,9
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..20000
Ilya Gutkovskiy, Scatterplot of partial sums of A348956
FORMULA
G.f. A(x) satisfies: A(x) = 1 - x^2 * A(x^2) + x^3 * A(x^3) - x^4 * A(x^4) + ...
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Sum[If[d < n, (-1)^(n/d + 1) a[d - 1], 0], {d, Divisors[n]}]; Table[a[n], {n, 0, 80}]
nmax = 80; A[_] = 0; Do[A[x_] = 1 - Sum[(-x)^k A[x^k], {k, 2, nmax}] + O[x]^(nmax + 1) //Normal, nmax + 1]; CoefficientList[A[x], x]
PROG
(PARI) A348956(n) = if(!n, 1, sumdiv(n, d, if(d<n, A348956(d-1)*(-1)^(1 + (n/d)), 0))); \\ Antti Karttunen, Nov 05 2021
CROSSREFS
KEYWORD
sign,look
AUTHOR
Ilya Gutkovskiy, Nov 04 2021
STATUS
approved