OFFSET
1,3
FORMULA
a(n) = A050452(4*n-3).
G.f.: Sum_{k>0} (4*k-1) * x^(3*k) / (1 - x^(4*k-1)).
MATHEMATICA
a[n_] := DivisorSum[4*n - 3, # &, Mod[#, 4] == 3 &]; Array[a, 100] (* Amiram Eldar, Jul 08 2023 *)
PROG
(PARI) a(n) = sumdiv(4*n-3, d, (d%4==3)*d);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 08 2023
STATUS
approved