A120377 Primes of the form 2*11^n-1.

241, 428717761

Offset

1,1

Comments

See comments for A057472. Examined in base 12, all n must be even and all primes must be 1-primes. For example, 241 is 181 in base 12.

The n<1000 that yield primes are 2, 8, 248. - T. D. Noe, Nov 16 2006

Links

Table of n, a(n) for n=1..2.

Formula

a(n) = n-th number such that 2*11^k-1 that is prime for some k.

a(n) = 2*11^A120378(n)-1. - R. J. Mathar, Mar 06 2010

Example

a(1)=241 since 2*11^2-1=241 is the first prime.

Maple

for w to 1 do for k from 1 to 2000 do n:=2*11^k-1; if isprime(n) then printf("%d, %d", k, n) fi od od;

Mathematica

Select[2*11^Range[1000]-1, PrimeQ] (* T. D. Noe, Nov 16 2006 *)

Crossrefs

Cf. A000043, A000668, A002957, A002959, A003307, A079363, A055558.

Sequence in context: A207286 A217998 A183891 * A321821 A171242 A259092

Adjacent sequences: A120374 A120375 A120376 * A120378 A120379 A120380

Keyword

nonn,bref

Author

Walter Kehowski, Jun 28 2006

Extensions

Corrected by T. D. Noe, Nov 16 2006

Status

approved