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A363857
Number of divisors of 7*n-5 of form 7*k+6.
7
0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 2, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 3, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 2, 0, 1, 1, 0, 0, 1, 0, 2, 0, 0, 0, 2, 1, 0, 1, 0, 0, 2, 0, 0, 0, 0, 1, 2, 0, 0, 1, 3, 0, 1, 0, 0, 1, 0, 0, 2, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0, 4, 0, 0, 0, 0, 1
OFFSET
1,23
COMMENTS
Also number of divisors of 7*n-5 of form 7*k+5.
FORMULA
a(n) = A363807(7*n-5) = A363808(7*n-5).
G.f.: Sum_{k>0} x^(5*k)/(1 - x^(7*k-1)).
G.f.: Sum_{k>0} x^(6*k-1)/(1 - x^(7*k-2)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 5, 1 &, Mod[#, 7] == 6 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-5, d, d%7==6);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 24 2023
STATUS
approved