OFFSET
1,4
COMMENTS
This is not multiplicative: a(4) = 4 and a(9) = 7, but a(36) = 31, not 28.
LINKS
MATHEMATICA
f1[p_, e_] := p + 1; f2[p_, e_] := p^e + 1; s[1] = 1; s[n_] := (Times @@ f1 @@@ (f = FactorInteger[n]) + Times @@ f2 @@@ f)/2; a[n_] := Denominator[DivisorSigma[1, n]/s[n]]; Array[a, 100] (* Amiram Eldar, Nov 06 2021 *)
PROG
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Antti Karttunen, Nov 06 2021
STATUS
approved