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A363973
Expansion of Sum_{k>0} k^2 * x^(4*k-1) / (1 - x^(4*k-1)).
1
0, 0, 1, 0, 0, 1, 4, 0, 1, 0, 9, 1, 0, 4, 17, 0, 0, 1, 25, 0, 5, 9, 36, 1, 0, 0, 50, 4, 0, 17, 64, 0, 10, 0, 85, 1, 0, 25, 101, 0, 0, 5, 121, 9, 17, 36, 144, 1, 4, 0, 170, 0, 0, 50, 205, 4, 26, 0, 225, 17, 0, 64, 261, 0, 0, 10, 289, 0, 37, 85, 324, 1, 0, 0, 378, 25, 13, 101, 400, 0, 50, 0
OFFSET
1,7
FORMULA
a(n) = Sum_{d|n, d==3 mod 4} ((d+1)/4)^2.
MATHEMATICA
a[n_] := DivisorSum[n, ((#+1)/4)^2 &, Mod[#, 4] == 3 &]; Array[a, 100] (* Amiram Eldar, Jun 30 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (d%4==3)*((d+1)/4)^2);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jun 30 2023
STATUS
approved