OFFSET
1,3
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..1001
MATHEMATICA
s[1] = 1; s[n_] := s[n] = -DivisorSum[n, s[#] * 2^(n/# - 1) &, # < n &]; a[n_] := DivisorSum[n, CatalanNumber[# - 1] * s[n/#] &]; Array[a, 32] (* Amiram Eldar, Nov 22 2021 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Nov 22 2021
STATUS
approved