OFFSET
1,7
FORMULA
a(n) = A363806(7*n-5).
G.f.: Sum_{k>0} x^(4*k-1)/(1 - x^(7*k-3)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 5, 1 &, Mod[#, 7] == 4 &]; Array[a, 100] (* Amiram Eldar, Jun 26 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-5, d, d%7==4);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 26 2023
STATUS
approved