A066807 Integers of the form (2^k+1)/k.

3, 3, 57, 4971027, 29850020237398251227313, 17503832475167772961878049926333027042428946479619, 58167804601757508792865761341330650726830745576152064464908846133090363

Offset: 1

Author

Benoit Cloitre, Jan 19 2002

Keywords

• nonn

Comments

The next term a(8) has 152 digits and a(9) has 217 digits. - Harvey P. Dale, Oct 20 2014

Links

• Amiram Eldar, Table of n, a(n) for n = 1..12

Crossrefs

Cf. A006521.

Programs

Mathematica

Select[Table[(2^n+1)/n,{n,300}],IntegerQ] (* Harvey P. Dale, Oct 20 2014 *)

PARI

lista(nn) = {for (n=1, nn, if (type(v = (2^n+1)/n) == "t_INT", print1(v, ", ")););} \\ Michel Marcus, Nov 20 2013

Formula

a(n) == 0 (mod 3).