

A107643


Numbers n such that the string 75n is prime.


0



1, 7, 17, 23, 29, 37, 41, 47, 49, 59, 61, 73, 77, 83, 89, 91, 109, 133, 149, 161, 167, 169, 181, 193, 209, 211, 217, 223, 227, 239, 253, 269, 277, 289, 307, 323, 329, 337, 347, 353, 367, 377, 389, 391, 401, 403, 407, 431, 437, 479, 503, 511, 521, 527
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


LINKS

Table of n, a(n) for n=1..54.


EXAMPLE

1 is a term as 751 is prime; 2 isn't, as 752 is composite; 37 is, as 7537 is prime.


PROG

(Sage) is_A107643 = lambda n: is_prime(Integer('75'+str(n))) # D. S. McNeil, Dec 10 2010
(MAGMA) [ n: n in [1..700]  IsPrime(Seqint(Intseq(n) cat [5, 7])) ]; // Vincenzo Librandi, Feb 02 2011


CROSSREFS

Cf. A107642.
Sequence in context: A239210 A191087 A032454 * A289363 A319040 A216838
Adjacent sequences: A107640 A107641 A107642 * A107644 A107645 A107646


KEYWORD

nonn,base,less


AUTHOR

Parthasarathy Nambi, Jun 09 2005


STATUS

approved



