This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A023250 #31 Mar 14 2025 15:29:44 %S A023250 2,7,11,37,67,89,109,149,179,257,439,467,571,677,691,719,929,977,1019, %T A023250 1279,1381,1447,1549,1567,1747,1787,1901,1931,2111,2161,2207,2287, %U A023250 2347,2377,2459,2539,2671,2711,2819,3119,3229,3371,3491,3607,3637,3821,3877 %N A023250 Primes that remain prime through 2 iterations of function f(x) = 4x + 3. %C A023250 Primes p such that 4*p+3 and 16*p+15 are also primes. - _Vincenzo Librandi_, Aug 04 2010 %H A023250 John Cerkan, <a href="/A023250/b023250.txt">Table of n, a(n) for n = 1..10000</a> %p A023250 A023250:=n->`if`(isprime(n) and isprime(4*n+3) and isprime(16*n+15), n, NULL): seq(A023250(n), n=1..10^4); # _Wesley Ivan Hurt_, Feb 12 2017 %t A023250 Select[Range@ 3900, Times @@ Boole@ PrimeQ@ NestList[4 # + 3 &, #, 2] > 0 &] (* _Michael De Vlieger_, Sep 13 2016 *) %o A023250 (Magma) [n: n in [0..100000] | IsPrime(n) and IsPrime(4*n+3) and IsPrime(16*n+15)]; // _Vincenzo Librandi_, Aug 04 2010 %Y A023250 Subsequence of A095278. %K A023250 nonn %O A023250 1,1 %A A023250 _David W. Wilson_