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A107645 Numbers n such that the string 1311n is the decimal expansion of a prime number. 4
11, 13, 29, 43, 49, 71, 103, 109, 127, 131, 143, 173, 181, 217, 223, 229, 239, 241, 251, 259, 263, 287, 301, 307, 311, 341, 353, 367, 377, 383, 403, 407, 419, 433, 449, 473, 481, 493, 503, 509, 523, 547, 553, 559, 577, 599, 617, 619, 623, 643, 689, 691 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

11 and 13 are twin primes.

LINKS

Table of n, a(n) for n=1..52.

EXAMPLE

n=71: 131171 is prime.

n=131: 1311131 is prime.

PROG

(MAGMA) [ n: n in [1..800] | IsPrime(Seqint(Intseq(n) cat [1, 1, 3, 1])) ];

CROSSREFS

Sequence in context: A115560 A045466 A158759 * A106014 A261371 A056251

Adjacent sequences:  A107642 A107643 A107644 * A107646 A107647 A107648

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Jun 09 2005

STATUS

approved

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Last modified May 24 21:25 EDT 2017. Contains 287008 sequences.