A069061 - OEIS

A069061

Sum of divisors of 2^n+1.

4, 6, 13, 18, 48, 84, 176, 258, 800, 1302, 2736, 4356, 10928, 20520, 51792, 65538, 174768, 351120, 699056, 1110276, 3100240, 5048232, 11184816, 17041416, 49012992, 82623888, 211053040, 284225796, 727960800, 1494039792, 2863311536, 4301668356, 12611914848, 20788904016

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OFFSET

1,1

LINKS

Max Alekseyev, Table of n, a(n) for n = 1..1122 (terms 1..1062 from Amiram Eldar)

FORMULA

a(n) = sigma(2^n+1).

a(n) = A000203(A000051(n)). - Michel Marcus, Nov 24 2013

MATHEMATICA

DivisorSigma[1, 2^Range[50] + 1] (* Paolo Xausa, Jul 05 2024 *)

PROG

(PARI) a(n) = sigma(2^n+1); \\ Michel Marcus, Nov 24 2013