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 A275203 #35 Jul 27 2016 10:52:54 %S A275203 1,2,4,64 %N A275203 Hyperoperations using consecutive integers. %C A275203 a(4) is too large to display. The number of decimal digits in (the number of decimal digits in a(4)) is approximately 64^64*log[10](64), that is, about 7.1*10^115. - _Robert Israel_, Jul 19 2016 %H A275203 Wikipedia, <a href="https://en.wikipedia.org/wiki/Hyperoperation">Hyperoperation</a> %F A275203 a(n) = H_n(a(n-1),n), where H_n is the n-th hyperoperation. %e A275203 a(0) = H_0(null,0) = 0+1 = 1. %e A275203 a(1) = H_1(1,1) = 1+1 = 2. %e A275203 a(2) = H_2(2,2) = 2*2 = 4. %e A275203 a(3) = H_3(4,3) = 4^3 = 64. %e A275203 a(4) = H_4(64,4) = 64^(64^(64^64)). %Y A275203 Cf. A189896, A264930. %K A275203 nonn %O A275203 0,2 %A A275203 _Tyler Skywalker_, Jul 19 2016