

A057708


Numbers n such that 2^n reversed is prime.


9



1, 4, 5, 7, 10, 17, 24, 37, 45, 55, 70, 77, 107, 137, 150, 271, 364, 1157, 1656, 2004, 2126, 3033, 3489, 3645, 4336, 6597, 7279, 12690, 13840, 20108, 21693, 28888, 84155, 102930
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OFFSET

1,2


COMMENTS

a(35) > 105000.  Giovanni Resta, Feb 22 2013


LINKS

Table of n, a(n) for n=1..34.


EXAMPLE

4 is a member because 2^4 reversed is 61 and prime.


MAPLE

with(numtheory): myarray := []: for n from 1 to 4000 do it1 := convert(2^n, base, 10): it2 := sum(10^(nops(it1)i)*it1[i], i=1..nops(it1)): if isprime(it2) then printf(`%d, `, n) fi: od:


MATHEMATICA

Do[ If[ PrimeQ[ FromDigits[ Reverse[ IntegerDigits[2^n]] ]], Print[ n]], {n, 20000}] (* Robert G. Wilson v, Jan 29 2005 *)


CROSSREFS

Sequence in context: A145018 A018910 A022936 * A032686 A074300 A047375
Adjacent sequences: A057705 A057706 A057707 * A057709 A057710 A057711


KEYWORD

base,nonn,more


AUTHOR

G. L. Honaker, Jr., Oct 23 2000


EXTENSIONS

More terms from Chris Nash (chris_nash(AT)prodigy.net), Oct 25 2000
Two more terms from Robert G. Wilson v, Jan 29 2001
3 more terms from Farideh Firoozbakht, Aug 05 2004
a(33)a(34) from Giovanni Resta, Feb 22 2013


STATUS

approved



