OFFSET
1,2
FORMULA
a(n) = A284281(5*n-1).
G.f.: Sum_{k>0} (5*k-2) * x^(3*k-1) / (1 - x^(5*k-2)).
MATHEMATICA
a[n_] := DivisorSum[5*n - 1, # &, Mod[#, 5] == 3 &]; Array[a, 100] (* Amiram Eldar, Jul 06 2023 *)
PROG
(PARI) a(n) = sumdiv(5*n-1, d, (d%5==3)*d);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 06 2023
STATUS
approved