OFFSET
1,2
FORMULA
a(n) = (1/2) * Sum_{d | 2*n-1} (d+1) = A007503(2*n-1)/2.
G.f.: Sum_{k>0} x^k / (1 - x^(2*k-1))^2.
MATHEMATICA
a[n_] := DivisorSum[2*n - 1, # + 1 &]/2; Array[a, 100] (* Amiram Eldar, Jul 04 2023*)
PROG
(PARI) a(n) = sumdiv(2*n-1, d, d+1)/2;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 04 2023
STATUS
approved