%I #15 Jul 25 2024 17:58:14
%S 4,10,14,20,26,40,110,124,146,206,250,326,340,350,436,440,470,634,686,
%T 704,920,1004,1054,1060,1124,1156,1246,1276,1294,1316,1376,1420,1550,
%U 1570,1654,1664,1784,1966,1970,2026,2116,2210,2380,2516,2594,2654,2780
%N Numbers k such that k^2 + 1 and k^2 - 3 are both prime.
%C This is the intersection of A028873 and A005574; this sequence is also a subset of A090120 (n such that closest primes above and below n^2 differ by 4).
%e a(2)=10 since 10^2 + 1 = 101 and 10^2 - 3 = 97 are both prime.
%t Select[Range[3,3000],AllTrue[#^2+{1,-3},PrimeQ]&] (* _Harvey P. Dale_, Jul 25 2024 *)
%o (Magma) [n: n in [2..100000] |IsPrime(n^2+1) and IsPrime(n^2-3)] // _Vincenzo Librandi_, Nov 13 2010
%Y Cf. A005574, A028873, A090120.
%K nonn
%O 1,1
%A _John L. Drost_, Feb 07 2006