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A363856
Number of divisors of 7*n-4 of form 7*k+6.
5
0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 2, 0, 0, 0, 2, 0, 2, 0, 1, 0, 0, 0, 2, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 3, 0, 1, 0, 1, 0, 1, 0, 2, 0, 0, 0, 2, 1, 0, 0, 1, 0, 2, 0, 2, 1, 0, 0, 3, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 3, 0, 0, 0, 2, 0, 1, 0, 1, 1, 1, 1, 2
OFFSET
1,16
COMMENTS
Also number of divisors of 7*n-4 of form 7*k+4.
FORMULA
a(n) = A363806(7*n-4) = A363808(7*n-4).
G.f.: Sum_{k>0} x^(4*k)/(1 - x^(7*k-1)).
G.f.: Sum_{k>0} x^(6*k-2)/(1 - x^(7*k-3)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 4, 1 &, Mod[#, 7] == 6 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-4, d, d%7==6);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 24 2023
STATUS
approved