%I
%S 319,337,357,363,371,387,409,447,591,663,681,701,801,827,893
%N Numbers n with property that n^2 is a concatenation of two 3digit primes.
%C There are exactly 15 such numbers.
%e Corresponding squares are: 101761, 113569, 127449, 131769, 137641, 149769, 167281, 199809, 349281, 439569, 463761, 491401, 641601, 683929, 797449.
%t c = 0; t = 1000; re = Sort[Reap[Do[If[PrimeQ[p], Do[If[PrimeQ[q], r = p*t + q; s = Sqrt[r]; If[s == Floor[s], c++; Sow[s]]], {q, 101, 999, 2}]], {p, 101, 999, 2}]][[2, 1]]]
%K fini,full,nonn,base
%O 1,1
%A _Zak Seidov_, Dec 17 2008
