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 A116889 #5 Nov 07 2013 02:53:22 %S A116889 2,3,3,5087,306167 %N A116889 a(n) is the least prime p that remains prime through n iterations of function f(p)=p^2+4. %C A116889 The sequence is finite, since it can be proved that if p, f(p), f(f(p)), f(f(f(p))) and f(f(f(f(p)))) are all primes, then the next iteration gives a multiple of 13, greater than 13, thus a(k) for k>=5 does not exist. %e A116889 a(0)=2 since f(2)=8 is not prime. a(1)=a(2)=3 since both f(3)=13 and f(f(3))=173 are primes. %Y A116889 Cf. A062324, A116886, A116887, A116888. %K A116889 fini,full,nonn %O A116889 0,1 %A A116889 _Giovanni Resta_, Feb 27 2006 %E A116889 Typo in Example fixed by _Zak Seidov_, Nov 07 2013