OFFSET
1,4
FORMULA
a(n) = (1/4) * Sum_{d | 4*n-2, d==3 (mod 4)} (d+1).
G.f.: Sum_{k>0} x^(3*k-1) / (1 - x^(4*k-2))^2.
MATHEMATICA
a[n_] := DivisorSum[4*n - 2, # + 1 &, Mod[#, 4] == 3 &]/4; Array[a, 100] (* Amiram Eldar, Jul 08 2023 *)
PROG
(PARI) a(n) = sumdiv(4*n-2, d, (d%4==3)*(d+1))/4;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 08 2023
STATUS
approved