login
A363880
Number of divisors of 7*n-6 of form 7*k+3.
0
0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 3, 0, 0, 1, 0, 1, 1, 0, 0, 1, 2, 0, 2, 0, 0, 2, 0, 0, 1, 0, 2, 1, 0, 0, 2, 1, 0, 1, 0, 1, 3, 0, 0, 1, 0, 1, 2, 0, 0, 1, 2, 0, 1, 0, 0, 2, 1, 0, 3, 0, 2, 1, 0, 0, 1, 1, 0, 1, 0, 0, 4, 0, 0, 2, 0, 1, 1, 1, 0, 1, 2, 0, 3, 0, 0, 2, 0, 0, 1, 0, 3, 1, 0
OFFSET
1,18
COMMENTS
Also number of divisors of 7*n-6 of form 7*k+5.
FORMULA
a(n) = A363805(7*n-6) = A363807(7*n-6).
G.f.: Sum_{k>0} x^(5*k-2)/(1 - x^(7*k-4)).
G.f.: Sum_{k>0} x^(3*k)/(1 - x^(7*k-2)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 6, 1 &, Mod[#, 7] == 3 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-6, d, d%7==3);
CROSSREFS
Sequence in context: A005890 A104515 A337923 * A324874 A324862 A324864
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 25 2023
STATUS
approved