OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
MATHEMATICA
Table[Total[Select[Divisors[n], Mod[#-1, 4]!=0&]]-n, {n, 90}] (* Harvey P. Dale, Jul 12 2024 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Jun 04 2019
STATUS
approved