OFFSET
1,14
COMMENTS
Also number of divisors of 7*n-2 of form 7*k+4.
FORMULA
MATHEMATICA
a[n_] := DivisorSum[7*n - 2, 1 &, Mod[#, 7] == 3 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-2, d, d%7==3);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 25 2023
STATUS
approved