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 A116887 #21 Aug 13 2025 03:22:05 %S A116887 5087,11173,16657,47017,54503,185243,207643,300413,306167,341813, %T A116887 391387,849047,1348577,1438223,1502923,1857407,1909267,2121737, %U A116887 2161163,2288773,2610133,2725157,2744723,2779097,2874463,2881327,3079927,3149077,3154483,3173683,3194483 %N A116887 Primes p that remain prime through at least 3 iterations of function f(p)=p^2+4. %H A116887 Zak Seidov, <a href="/A116887/b116887.txt">Table of n, a(n) for n = 1..2567</a> (all terms up to 10^9). %e A116887 p=5087, f(p)= 25877573, f(f(p))= 669648784370333 and f(f(f(p)))= 448429494408664742387290530893 are all primes. %t A116887 Select[Prime[Range[8! ]],PrimeQ[ #^2+4]&&PrimeQ[(#^2+4)^2+4]&&PrimeQ[ ((#^2+4)^2+4)^2+4]&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 26 2010 *) %Y A116887 Cf. A062324, A116886, A116888, A116889. %K A116887 nonn %O A116887 1,1 %A A116887 _Giovanni Resta_, Feb 27 2006