A103630 Numbers n such that the string 235n is the decimal expansion of a prime number.

1, 7, 31, 37, 39, 49, 57, 61, 63, 67, 81, 93, 99, 111, 117, 159, 171, 177, 181, 199, 211, 231, 241, 243, 273, 289, 307, 309, 337, 349, 369, 397, 439, 441, 447, 483, 489, 493, 513, 519, 523, 537, 541, 553, 559, 577, 591, 601, 607, 621, 661, 663, 673, 679, 699

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

1 is in the sequence because 2351 is prime.
49 is in the sequence because 23549 is prime.
171 is in the sequence because 235171 is prime.

Maple

map(p->p[2], select(p -> isprime(235*10^p[1]+p[2]), [seq([1, k], k=1..9, 2), seq(seq([d, k], k=10^(d-1)+1..10^d, 2), d=2..3)])); # Robert Israel, Jan 11 2018

Prog

(Magma) [ n: n in [1..800] | IsPrime(Seqint(Intseq(n) cat [5, 3, 2])) ]; // Klaus Brockhaus, Feb 02 2011

Crossrefs

Sequence in context: A122654 A184121 A167768 * A205711 A040064 A241101

Adjacent sequences: A103627 A103628 A103629 * A103631 A103632 A103633

Keyword

base,nonn

Author

Parthasarathy Nambi, Mar 25 2005

Status

approved