A363359 - OEIS

A363359

Sum of divisors of 4*n-1 of form 4*k+3.

3, 7, 11, 18, 19, 23, 30, 31, 42, 42, 43, 47, 54, 66, 59, 73, 67, 71, 93, 79, 83, 90, 98, 114, 113, 103, 107, 114, 138, 126, 126, 127, 131, 180, 139, 154, 157, 151, 186, 162, 163, 167, 193, 217, 179, 186, 198, 191, 252, 199, 210, 233, 211, 258, 222, 223, 227, 252, 282, 239, 273, 266, 251, 324, 266, 263, 270

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..67.

FORMULA

a(n) = A050452(4*n-1).

G.f.: Sum_{k>0} (4*k-1) * x^k / (1 - x^(4*k-1)).

MATHEMATICA

a[n_] := DivisorSum[4*n - 1, # &, Mod[#, 4] == 3 &]; Array[a, 100] (* Amiram Eldar, Jul 08 2023 *)

PROG

(PARI) a(n) = sumdiv(4*n-1, d, (d%4==3)*d);