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 A364270 #23 Dec 12 2023 20:58:46 %S A364270 2,5,31,7625597485003 %N A364270 a(n) = 2^^n + 3^^n, where ^^ indicates tetration. %C A364270 a(4) has 3638334640025 digits and is too large to show here. %C A364270 a(n) is prime for n = 0, 1, 2, 3, but it is not known if a(4) is prime. %F A364270 a(n) = A014221(n) + A014222(n+1). %F A364270 a(n) = A321312(2,n) + A321312(3,n). %e A364270 For n = 3, a(3) = 2^2^2 + 3^3^3 = 2^4 + 3^27 = 7625597485003. %t A364270 nmax=3; NestList[2^#&, 1,nmax]+NestList[3^#&,1,nmax] (* _Stefano Spezia_, Oct 22 2023 *) %Y A364270 Cf. A004249, A014221, A014222, A321312. %K A364270 nonn,base,hard %O A364270 0,1 %A A364270 _Marco Ripà_, Oct 20 2023