OFFSET
1,4
FORMULA
a(n) = A284103(5*n-4).
G.f.: Sum_{k>0} (5*k-1) * x^(4*k) / (1 - x^(5*k-1)).
MATHEMATICA
a[n_] := DivisorSum[5*n - 4, # &, Mod[#, 5] == 4 &]; Array[a, 100] (* Amiram Eldar, Jul 17 2023 *)
PROG
(PARI) a(n) = sumdiv(5*n-4, d, (d%5==4)*d);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 04 2023
STATUS
approved