A112636 Numbers k such that sigma(2^k+3^k) is divisible by k.

1, 2, 3, 14, 24, 28, 48, 72, 84, 132, 140, 144, 154, 155, 165, 180, 192, 196, 203, 208, 216, 252, 272, 320, 352, 360, 384, 396, 399, 420, 432, 448, 465, 468, 536

Offset

1,2

Comments

a(22) > 235. - Giovanni Resta, Mar 25 2013

Links

Table of n, a(n) for n=1..35.

Formula

k | sigma(2^k+3^k).

Example

14 is a term because 2^14+3^14 = 4799353 with divisors {1,13,369181,4799353} sum of which is 5168548 = 14*369182.

Prog

(PARI) for(x=1, 200, if(sigma(2^x+3^x)%x==0, print1(x, ", "))) \\ Jorge Coveiro, Feb 15 2006

Crossrefs

Cf. A000203 (sigma), A007689 (2^n + 3^n), A114705 (sigma(2^n + 3^n)).

Sequence in context: A025092 A047067 A188533 * A124663 A101005 A029998

Adjacent sequences: A112633 A112634 A112635 * A112637 A112638 A112639

Keyword

nonn,more

Author

Zak Seidov, Dec 27 2005

Extensions

3 more terms from Jorge Coveiro, Feb 15 2006

More terms from Ryan Propper, Jan 09 2007

a(19)-a(21) from Giovanni Resta, Mar 25 2013

Data corrected and a(22)-a(44) added by Amiram Eldar, Dec 19 2019

Status

approved