OFFSET
1,5
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
If p odd prime, a(p) = (1-p)/2. - Bernard Schott, Nov 19 2021
MATHEMATICA
k[n_] := (n / 2^IntegerExponent[n, 2] + 1)/2; kinv[1] = 1; kinv[n_] := kinv[n] = -DivisorSum[n, kinv[#]*k[n/#] &, # < n &]; a[n_] := DivisorSum[n, IntegerExponent[2*#, 2]*kinv[n/#] &]; Array[a, 100] (* Amiram Eldar, Nov 19 2021 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Nov 18 2021
STATUS
approved