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A363852
Number of divisors of 7*n-5 of form 7*k+1.
2
1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 2, 1, 3, 2, 2, 1, 2, 1, 2, 1, 3, 1, 3, 1, 2, 1, 2, 1, 4, 1, 2, 2, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 2, 4, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 1, 2, 1, 4, 1, 4, 1, 2, 1, 2, 1, 3, 2, 3, 1, 2, 1, 2, 2, 2, 1, 5, 1, 2, 1, 2, 1, 2, 1, 3, 2, 2, 1, 4, 2, 2, 1, 4, 1
OFFSET
1,3
COMMENTS
Also number of divisors of 7*n-5 of form 7*k+2.
FORMULA
a(n) = A279061(7*n-5) = A363795(7*n-5).
G.f.: Sum_{k>0} x^(2*k-1)/(1 - x^(7*k-6)).
G.f.: Sum_{k>0} x^k/(1 - x^(7*k-5)).
MATHEMATICA
a[n_] := DivisorSum[7*n - 5, 1 &, Mod[#, 7] == 1 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)
PROG
(PARI) a(n) = sumdiv(7*n-5, d, d%7==1);
CROSSREFS
Sequence in context: A323287 A167679 A051881 * A357859 A338731 A081757
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 24 2023
STATUS
approved