OFFSET
1,7
COMMENTS
Also number of divisors of 7*n-1 of form 7*k+3.
FORMULA
MATHEMATICA
a[n_] := DivisorSum[7*n - 1, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-1, d, d%7==2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 24 2023
STATUS
approved