A111149 - OEIS

%I #16 Aug 18 2025 18:33:48

%S 2,4,10,16,26,28,38,40,44,46,58,70,80,82,88,94,98,110,116,128,130,136,

%T 140,142,154,164,178,194,200,208,212,214,220,224,236,248,250,254,256,

%U 268,278,284,298,310,320,322,332,334,338,362,392,406,422,424,458,460

%N Numbers k such that 5*k^2 + 9 is prime.

%H Robert Israel, <a href="/A111149/b111149.txt">Table of n, a(n) for n = 1..10000</a>

%e If k=154 then 5*k^2 + 9 = 118589 (prime).

%p select(k -> isprime(5*k ^2+ 9), [seq(k,k=0..1000,2)]); # _Robert Israel_, Aug 18 2025

%t Select[Range[500], PrimeQ[5*#^2 + 9] &] (* _Stefan Steinerberger_, Feb 26 2006 *)

%o (PARI) is(n)=isprime(5*n^2+9) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,easy

%O 1,1

%A _Parthasarathy Nambi_, Oct 18 2005

%E More terms from _Stefan Steinerberger_, Feb 26 2006