

A281923


Least prime p such that p^n is a concatenation of two primes.


2



23, 5, 3, 7, 3, 3, 43, 47, 3, 3, 7, 11, 17, 11, 3, 29, 3, 11, 3, 109, 11, 43, 71, 19, 71, 11, 11, 3, 7, 229, 43, 269, 7, 23, 3, 61, 37, 677, 113, 863, 59, 3, 11, 487, 359, 347, 3, 19, 53, 173, 3, 127, 229, 7, 3, 3, 13, 3, 241, 41, 79, 79, 3, 83, 23, 31, 71, 31
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


LINKS



EXAMPLE

a(1) = 23 because 23^1 = 23 = concat(2,3);
a(2) = 5 because 5^2 = 25 = concat(2,5);
a(3) = 3 because 3^3 = 27 = concat(2,7).


MAPLE

with(numtheory): P:= proc(q) local a, k, n, ok;
for n from 1 to q do for a from 1 by 2 to q do if isprime(a) then ok:=0;
for k from 1 to ilog10(a^n) do if isprime(trunc(a^n/10^k)) and isprime(a^n mod 10^k) then ok:=1; break; fi; od; if ok=1 then print(a); break; fi; fi; od; od; end: P(10^9);


CROSSREFS



KEYWORD

nonn,base,easy


AUTHOR



STATUS

approved



