OFFSET
1,8
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..2047 (computed from the b-file of A000001; a(1024) corrected by Andrey Zabolotskiy)
Wikipedia, Dirichlet convolution (Dirichlet inverse)
FORMULA
a(1) = 1; for n > 1, a(n) = -Sum_{d|n, d<n} A000001(n/d)*a(d). - Antti Karttunen, Jun 13 2018
MATHEMATICA
a[1] = 1; a[n_] := a[n] = -Sum[FiniteGroupCount[n/k] a[k], {k, Drop[Divisors[n], -1]}]; Table[a[n], {n, 100}]
PROG
CROSSREFS
KEYWORD
sign,hard
AUTHOR
Ben Branman, Mar 01 2012
EXTENSIONS
More terms from Antti Karttunen, Jun 13 2018
STATUS
approved