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%I #16 Jun 24 2016 10:36:09
%S 5,89,401,601,809,1609,2801,4649,5281,6569,9241,9929,14369,18089,
%T 19961,21841,27529,33289,41081,43049,51001,61121,67289,73529,79841,
%U 84089,92681,94849
%N Primes that becomes a square when prefixed with a 2.
%H Vincenzo Librandi and David A. Corneth, <a href="/A167735/b167735.txt">Table of n, a(n) for n = 1..10488</a> (First 222 terms from Vincenzo Librandi)
%t Select[Prime[Range[10000]],IntegerQ[Sqrt[FromDigits[Join[{2},IntegerDigits[#]]]]]&] (* _Harvey P. Dale_, Dec 16 2010 *)
%o (PARI) \\ terms upto 10^n
%o upto(n) = {my(sqrt21 = sqrt(2.1), sqrt30 = sqrt(3.0),r,t=0);
%o for(k=2, n, for(j = ceil((sqrt21 * sqrt(10^k))), floor(sqrt30 * sqrt(10^k)),
%o r = j^2%10^k; if(isprime(r),t++;print1(r", "))));t} \\ _David A. Corneth_, Jun 24 2016
%Y Cf. A167734, A167736, A167737, A167738, A167739, A167740, A167741.
%K base,nonn
%O 1,1
%A _Claudio Meller_, Nov 10 2009
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