A167736 Primes that become squares when prefixed with a 3.

61, 4969, 6481, 9601, 23761, 26041, 37561, 68449, 88129, 129361, 179089, 214849, 265249, 301489, 308761, 411409, 455881, 463321, 485689, 508129, 523129, 530641, 659569, 713329, 751969, 829849, 916441, 924361, 948169, 964081, 996001, 1058329, 1147561, 1281649

Offset: 1

Author

Claudio Meller, Nov 10 2009

Keywords

• base
• nonn
• changed

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..20000 (first 107 terms from Vincenzo Librandi)

Crossrefs

Cf. A167734, A167735, A167737, A167738, A167739, A167740, A167741.

Programs

Mathematica

Select[Prime[Range[1000000]],IntegerQ[Sqrt[FromDigits[Join[{3}, IntegerDigits[ #]]]]]&] (* Harvey P. Dale, Nov 01 2011 *)

PARI

\\ terms upto 10^n
upto(n) = {my(sqrt31 = sqrt(3.1), sqrt40 = sqrt(4.0), r); for(k=2, n, for(j = ceil((sqrt31 * sqrt(10^k))), floor(sqrt40 * sqrt(10^k)), r = j^2%10^k; if(isprime(r), print1(r", "))))} \\ David A. Corneth, Jun 24 2016

Extensions

More terms from Harvey P. Dale, Nov 01 2011