|
%I #6 Nov 11 2020 15:37:57
%S 3,6,9,12,21,30,33,36,45,48,60,69,72,75,81,87,99,108,111,114,117,120,
%T 123,126,129,153,165,168,174,177,183,201,204,207,222,234,243,252,267,
%U 279,282,285,294,303,312,315,318,339,345,348,369,378,381,384,393,396
%N Numbers n such that 10n^2 - 1 is prime.
%t p = 10; a = {}; Do[k = p x^2 - 1; If[PrimeQ[k], AppendTo[a, x]], {x, 1, 1000}]; a
%t Select[Range[500],PrimeQ[10#^2-1]&] (* _Harvey P. Dale_, Nov 11 2020 *)
%o (PARI) is(n)=isprime(10*n^2-1) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y A066436, A066049, A090686, A090684, A143826, A143827, A143828
%K nonn
%O 1,1
%A _Artur Jasinski_, Sep 02 2008
|
