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A270237
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Primes which are the decimal concatenation of 1, a prime, and 1.
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1
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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
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OFFSET
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1,1
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COMMENTS
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No padding 0's are allowed: 1021 is not a member even though 02 is prime.
These are the primes that result from A069687.
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LINKS
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EXAMPLE
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1171 is a prime which is the concatenation of 1, 17 and 1.
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MATHEMATICA
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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 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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