

A268111


Integers k such that the concatenation of 2^k and 3^k is prime.


0



0, 1, 3, 7, 8, 21, 23, 33, 51, 88, 96, 227, 287, 1231, 1924, 3035
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OFFSET

1,3


COMMENTS

First five primes: 11, 23, 827, 1282187, 2566561.


LINKS

Table of n, a(n) for n=1..16.


EXAMPLE

For k = 3 we have 2^3 and 3^3 equal to 8 and 27, respectively, and 827 is a prime number.


MATHEMATICA

Select[Range[100], PrimeQ[FromDigits[Join[IntegerDigits[2^#], IntegerDigits[3^#]]]] &] (* Alonso del Arte, Jan 27 2016 *)


PROG

(PARI) isok(n) = isprime(eval(concat(Str(2^n), Str(3^n)))); \\ Michel Marcus, Jan 26 2016


CROSSREFS

Cf. A000079, A000244.
Sequence in context: A259571 A291212 A125570 * A244532 A037208 A102007
Adjacent sequences: A268108 A268109 A268110 * A268112 A268113 A268114


KEYWORD

nonn,base,more


AUTHOR

Emre APARI, Jan 26 2016


EXTENSIONS

a(12)a(13) from Michel Marcus, Jan 26 2016


STATUS

approved



