A364103 Sum of divisors of 5*n-4 of form 5*k+4.
0, 0, 0, 4, 0, 0, 0, 13, 0, 0, 0, 18, 0, 0, 0, 23, 9, 0, 0, 28, 0, 0, 0, 33, 0, 23, 0, 38, 0, 0, 0, 43, 0, 0, 28, 48, 0, 0, 0, 67, 0, 0, 0, 91, 0, 0, 0, 63, 0, 0, 0, 68, 38, 33, 0, 73, 0, 0, 0, 78, 0, 43, 0, 83, 0, 0, 0, 126, 0, 0, 48, 93, 19, 0, 0, 98, 0, 0, 0, 156, 0, 43, 0, 108, 0, 0, 0, 113, 58
Offset: 1
Keywords
Programs
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Mathematica
a[n_] := DivisorSum[5*n - 4, # &, Mod[#, 5] == 4 &]; Array[a, 100] (* Amiram Eldar, Jul 17 2023 *)
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PARI
a(n) = sumdiv(5*n-4, d, (d%5==4)*d);
Formula
a(n) = A284103(5*n-4).
G.f.: Sum_{k>0} (5*k-1) * x^(4*k) / (1 - x^(5*k-1)).