A108101 Numbers k such that the string 1131k is the decimal expansion of a prime number.

1, 7, 11, 17, 23, 31, 43, 47, 49, 53, 59, 61, 67, 71, 73, 77, 89, 103, 113, 121, 131, 133, 139, 157, 181, 191, 217, 223, 239, 253, 259, 269, 271, 307, 323, 329, 331, 341, 343, 353, 379, 397, 413, 419, 421, 437, 451, 463, 467, 479, 491, 509, 523, 547, 553, 569

Offset

1,2

Comments

11 and 31 are primes.

471 out of the first 1000 terms of this sequence are prime. - Harvey P. Dale, Jul 07 2012

Links

Table of n, a(n) for n=1..56.

Example

11311 is prime, so 1 is a term.
113153 is prime, so 53 is a term.

Mathematica

With[{c={1, 1, 3, 1}}, Select[Range[600], PrimeQ[FromDigits[ Join[ c, IntegerDigits[ #]]]]&]]  (* Harvey P. Dale, Jul 07 2012 *)

Prog

(Magma) [ n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [1, 3, 1, 1])) ];

Crossrefs

Cf. A107645, A107644.

Sequence in context: A131229 A092737 A072669 * A158350 A048203 A370009

Adjacent sequences: A108098 A108099 A108100 * A108102 A108103 A108104

Keyword

nonn,base

Author

Parthasarathy Nambi, Jun 25 2005

Status

approved