OFFSET
1,3
FORMULA
a(n) = Sum_{d|n, d==1 mod 2} ((d+1)/2)^2.
MATHEMATICA
a[n_] := DivisorSum[n, ((# + 1)/2)^2 &, OddQ[#] &]; Array[a, 100] (* Amiram Eldar, Jun 30 2023 *)
PROG
(PARI) a(n) = sumdiv(n, d, (d%2==1)*((d+1)/2)^2);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jun 30 2023
STATUS
approved