login
A363972
Expansion of Sum_{k>0} k^2 * x^(4*k-3) / (1 - x^(4*k-3)).
1
1, 1, 1, 1, 5, 1, 1, 1, 10, 5, 1, 1, 17, 1, 5, 1, 26, 10, 1, 5, 37, 1, 1, 1, 54, 17, 10, 1, 65, 5, 1, 1, 82, 26, 5, 10, 101, 1, 17, 5, 122, 37, 1, 1, 158, 1, 1, 1, 170, 54, 26, 17, 197, 10, 5, 1, 226, 65, 1, 5, 257, 1, 46, 1, 310, 82, 1, 26, 325, 5, 1, 10, 362, 101, 54, 1, 401, 17, 1, 5, 451, 122, 1
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