A363885 Number of divisors of 7*n-3 of form 7*k+2.
1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 1, 2, 0, 2, 0, 2, 0, 2, 0, 4, 0, 2, 0, 2, 0, 2, 0, 2, 2, 2, 0, 2, 0, 2, 0, 3, 0, 4, 0, 2, 0, 2, 0, 2, 0, 2, 2, 2, 0, 2, 0, 4, 0, 2, 0, 4, 0, 2, 0, 2, 0, 2, 0, 2, 2, 2, 0, 4, 0, 2, 0, 2, 0, 4, 1, 2, 0, 2, 0, 2, 0, 2, 2, 4, 0, 2, 0, 2, 0, 2, 0, 4, 0, 2, 0, 2, 0, 4, 0
Offset: 1
Keywords
Programs
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Mathematica
a[n_] := DivisorSum[7*n - 3, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 26 2023 *)
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PARI
a(n) = sumdiv(7*n-3, d, d%7==2);
Formula
a(n) = A363795(7*n-3).
G.f.: Sum_{k>0} x^(2*k-1)/(1 - x^(7*k-5)).