OFFSET
1,5
FORMULA
a(n) = Sum_{d|n, d==1 mod 4} ((d+3)/4)^2.
MATHEMATICA
a[n_] := DivisorSum[n, ((#+3)/4)^2 &, Mod[#, 4] == 1 &]; Array[a, 100] (* Amiram Eldar, Jun 30 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (d%4==1)*((d+3)/4)^2);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jun 30 2023
STATUS
approved