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A270237 Primes which are the decimal concatenation of 1, a prime, and 1. 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 (list; graph; refs; listen; history; text; internal format)
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 A132254 A087832

Adjacent sequences:  A270234 A270235 A270236 * A270238 A270239 A270240

KEYWORD

nonn,base

AUTHOR

Emre APARI, Mar 13 2016

STATUS

approved

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Last modified January 18 21:06 EST 2021. Contains 340262 sequences. (Running on oeis4.)