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 A116888 #10 Nov 20 2023 11:45:04 %S A116888 306167,48639197,64695713,68252687,87788237,87813293,160486967, %T A116888 255974437,283032247,324609913,361705873,417684523,449364197, %U A116888 451995587,454052213,466037563,536504713,574746467,596095613 %N A116888 Primes p that remain prime through 4 iterations of the function f(p) = p^2 + 4. %e A116888 p = 306167, f(p) = 93738231893, f(f(p)) = 8786856118425842363453, f(f(f(p))) = 77208840445917661077402487029419236950083213 and the 88-digit number f(f(f(f(p)))) are all prime numbers. %t A116888 Select[Prime[Range[9! ]],PrimeQ[ #^2+4]&&PrimeQ[(#^2+4)^2+4]&&PrimeQ[((#^2+4)^2+4)^2+4]&&PrimeQ[(((#^2+4)^2+4)^2+4)^2+4]&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 26 2010 *) %t A116888 p4Q[p_]:=AllTrue[NestList[#^2+4&,p,4],PrimeQ]; Select[Prime[Range[312*10^5]],p4Q] (* _Harvey P. Dale_, Nov 20 2023 *) %Y A116888 Cf. A062324, A116886, A116887, A116889. %K A116888 nonn %O A116888 1,1 %A A116888 _Giovanni Resta_, Feb 27 2006