OFFSET
1,4
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
a[n_] := DivisorSum[n, # + 2 &, Mod[#, 3] == 1 &]/3; Array[a, 100] (* Amiram Eldar, Jun 27 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (d%3==1)*(d+2))/3;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 27 2023
STATUS
approved