OFFSET
1,19
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A319995(6*n-4).
G.f.: Sum_{k>0} x^(4*k)/(1 - x^(6*k-1)).
G.f.: Sum_{k>0} x^(5*k-1)/(1 - x^(6*k-2)).
MATHEMATICA
a[n_] := DivisorSum[6*n-4, 1 &, Mod[#, 6] == 5 &]; Array[a, 100] (* Amiram Eldar, Aug 14 2023 *)
PROG
(PARI) a(n) = sumdiv(6*n-4, d, d%6==5);
(PARI) my(N=100, x='x+O('x^N)); concat([0, 0, 0], Vec(sum(k=1, N, x^(4*k)/(1-x^(6*k-1)))))
(PARI) my(N=100, x='x+O('x^N)); concat([0, 0, 0], Vec(sum(k=1, N, x^(5*k-1)/(1-x^(6*k-2)))))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 25 2022
STATUS
approved