A243886 - OEIS

A243886

Primes p = prime(n): such that p.n and n.p both are prime, where (.) indicates concatenation.

661, 1051, 1999, 2179, 3433, 3593, 3719, 4073, 4591, 4733, 5449, 5503, 6079, 6481, 7109, 7211, 7489, 8293, 8513, 9901, 10273, 10529, 11821, 12721, 14107, 14591, 14879, 15263, 15877, 18149, 19559, 22027, 22129, 22571, 23339, 24527, 25357, 26881, 27337, 34259

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OFFSET

1,1

COMMENTS

Intersection of A084671 and A166283.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

661 is in the sequence because 661 = prime(121): Concatenations of [661.121 = 661121] and concatenation of [121.661 = 121661] which are also primes.

1051 is in the sequence because 1051 = prime(177): Concatenation of [1051.177 = 1051177] and concatenation of [177.1051 = 1771051] which are also primes.

MAPLE

with(numtheory): with(StringTools): A243886:= proc() local p, k1, k2; p:=ithprime(n); k1:=parse (cat (p, n)); k2:=parse(cat(n, p)); if isprime(k1)and isprime(k2) then RETURN (p); fi; end: seq(A243886 (), n=1..5000);

MATHEMATICA

Select[Prime [Range[5000]], PrimeQ[FromDigits[Join[IntegerDigits [PrimePi [#]], IntegerDigits [#]]]] && PrimeQ [FromDigits [Join [IntegerDigits[#], IntegerDigits [PrimePi [#]]]]] &]

CROSSREFS

Cf. A000040, A084671, A166283.

Sequence in context: A252449 A252401 A171394 * A145750 A243889 A105978

Adjacent sequences: A243883 A243884 A243885 * A243887 A243888 A243889

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Jun 13 2014

STATUS

approved