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

Author

Emre APARI, Mar 13 2016

Keywords

• nonn
• base

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.

Examples

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

Links

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

Crossrefs

Cf. A000040, A069687, A208259.

Programs

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 *)

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