A102504 Values of n for which the concatenations 1nn1, 3nn3, 7nn7 and 9nn9 are all primes.

2092, 2131, 2797, 3433, 4126, 5524, 5710, 6817, 8383, 8815, 9472, 114613, 116329, 130213, 206776, 239389, 282298, 286642, 306046, 307180, 311317, 318310, 341386, 360733, 366529, 377005, 425665, 430597, 460441, 475642, 475660, 478078, 490870

Offset

1,1

Links

Table of n, a(n) for n=1..33.

Example

E.g. n=2092 leads to 1209220921, 3209220923, 7209220927 and 9209220929, all of which are primes.

Mathematica

foQ[n_, o_] := Block[{id = IntegerDigits[n]}, PrimeQ[ FromDigits[ Join[{o}, id, id, {o}] ]]]; Select[ Range[500985], foQ[ #, 1] && foQ[ #, 3] && foQ[ #, 7] && foQ[ #, 9] &] (* Robert G. Wilson v, Jan 14 2005 *)

Crossrefs

For full sequences of integers of form 1nn1 (A100846), 3nn3 (A100896), 7nn7 (A100897), 9nn9 (A102484). For primes in these sequences: 1nn1 (A102496, A102497), 3nn3 (A102498, A102499), 7nn7 (A102500, A102501), 9nn9 (A102502, A102503).

Sequence in context: A206606 A089159 A045051 * A270761 A332643 A015293

Adjacent sequences: A102501 A102502 A102503 * A102505 A102506 A102507

Keyword

easy,nonn,base

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

Status

approved