A270237 Primes which are the decimal concatenation of 1, a prime, and 1.

131, 151, 1171, 1231, 1291, 1471, 1531, 1831, 11071, 11131, 11311, 11491, 11731, 11971, 12391, 12511, 13171, 13591, 13831, 14011, 14431, 15031, 15091, 15991, 16411, 16831, 17011, 17191, 17431, 17971, 18211, 19471, 19531, 110311, 110491, 111031, 111091, 111871

Offset

1,1

Comments

No padding 0's are allowed: 1021 is not a member even though 02 is prime.

These are the primes that result from A069687.

Subsequence of A208259.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

1171 is a prime which is the concatenation of 1, 17 and 1.

Mathematica

Select[Map[FromDigits@ Flatten@ {1, IntegerDigits@ Prime@ #, 1} &, Range@ 200], PrimeQ] (* Michael De Vlieger, Mar 15 2016 *)
Select[FromDigits[Flatten[IntegerDigits/@Join[{1}, #, {1}]]]&/@Prime[ Range[ 200]], PrimeQ] (* Harvey P. Dale, Jul 26 2016 *)

Prog

(PARI) lista(nn) = forprime(p=2, nn, if(isprime(P=eval(Str(1, p, 1))), print1(P, ", "))); \\ Altug Alkan, Mar 13 2016
(PARI) is(n)=my(d=digits(n)); isprime(n) && d[1]==1 && #d>2 && d[2] && d[#d]==1 && isprime(fromdigits(d[2..#d-1])) \\ Charles R Greathouse IV, Mar 15 2016

Crossrefs

Cf. A000040, A069687, A208259.

Sequence in context: A173071 A164294 A155924 * A090264 A345520 A345774

Adjacent sequences: A270234 A270235 A270236 * A270238 A270239 A270240

Keyword

nonn,base

Author

Emre APARI, Mar 13 2016

Status

approved