A167720 Squares that become a prime number when prefixed with a 5.

9, 441, 1521, 12321, 19881, 29241, 59049, 74529, 95481, 123201, 168921, 199809, 227529, 263169, 288369, 328329, 356409, 370881, 385641, 471969, 480249, 488601, 531441, 558009, 594441, 603729, 613089, 622521, 690561, 741321, 804609, 826281

Offset: 1

Author

Claudio Meller, Nov 10 2009

Keywords

• base
• nonn

Comments

Subsequence of squares of A032668. - Michel Marcus, Jun 21 2016

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A032668.

Programs

Mathematica

Select[Range[1, 500, 2]^2, PrimeQ[FromDigits[Join[{5}, IntegerDigits[#]]]] &] (* G. C. Greubel, Jun 20 2016 *)