A374237 -id:A374237 - cp's OEIS frontend

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

Offset: 1

Benoit Cloitre, Apr 04 2002

nonn

Max Alekseyev, Table of n, a(n) for n = 1..1128 (terms 1..1062 from Amiram Eldar)

Cf. A000051, A000203, A002185, A002587, A002589, A046798, A046799, A053285, A054992, A057957, A059886, A085029, A086257, A112092, A250291, A274906, A295501.

Row sums of A374237.

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

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

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

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

More terms from Amiram Eldar, Oct 04 2019

A361438 Triangle T(n,k), n >= 1, 1 <= k <= A046801(n), read by rows, where T(n,k) is k-th smallest divisor of 2^n-1.

Original entry on oeis.org

1, 1, 3, 1, 7, 1, 3, 5, 15, 1, 31, 1, 3, 7, 9, 21, 63, 1, 127, 1, 3, 5, 15, 17, 51, 85, 255, 1, 7, 73, 511, 1, 3, 11, 31, 33, 93, 341, 1023, 1, 23, 89, 2047, 1, 3, 5, 7, 9, 13, 15, 21, 35, 39, 45, 63, 65, 91, 105, 117, 195, 273, 315, 455, 585, 819, 1365, 4095, 1, 8191, 1, 3, 43, 127, 129, 381, 5461, 16383

Offset: 1

Seiichi Manyama, Mar 12 2023

			Triangle begins:
  1;
  1,   3;
  1,   7;
  1,   3,  5,   15;
  1,  31;
  1,   3,  7,    9, 21, 63;
  1, 127;
  1,   3,  5,   15, 17, 51,  85,  255;
  1,   7, 73,  511;
  1,   3, 11,   31, 33, 93, 341, 1023;
  1,  23, 89, 2047;

Seiichi Manyama, Rows n = 1..64, flattened
Index entries for sequences related to divisors of numbers

Subsequence of A027750.
Cf. A000225, A049479 (2nd column), A075708 (row sums).
Cf. A374237 (analogous for 2^n + 1).

T:= n-> sort([numtheory[divisors](2^n-1)[]])[]:
seq(T(n), n=1..12);  # Alois P. Heinz, Oct 20 2024

Divisors[2^Range[15] - 1] (* Paolo Xausa, Jul 02 2024 *)

cp's OEIS Frontend

A069061 Sum of divisors of 2^n+1.

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