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 A271976 #11 Jan 11 2020 15:57:47 %S A271976 20,7625597485013, %T A271976 13407807929942597099574024998205846127479365820592393377723561443721764030073546976801874298166903427690031858186486050853753882811946569946433649006084137 %N A271976 a(n) = G_n(20), where G is the Goodstein function defined in A266201. %e A271976 G_1(20) = B_2(20)-1 = B_2(2^2^2+2^2)-1 = 3^3^3+3^3-1 = 7625597485013; %e A271976 G_2(20) = B_3(3^3^3+2*3^2+2*3+2)-1 = 4^4^4+2*4^2+2*4+2-1 has 154 digits; %e A271976 G_3(20) = B_4(4^4^4+2*4^2+2*4+1)-1 = 5^5^5+2*5^2+2*5+1-1 has 2184 digits. %Y A271976 Cf. A056193: G_n(4), A059933: G_n(16), A211378: G_n(19), A215409: G_n(3), A222117: G_n(15), A266204: G_n(5), A266205: G_n(6), A271554: G_n(7), A271555: G_n(8), A271556: G_n(9), A271557: G_n(10), A271558: G_n(11), A271559: G_n(12), A271560: G_n(13), A271561: G_n(14), A271562: G_n(17), A271975: G_n(18), A266201: G_n(n). %K A271976 nonn,fini,less %O A271976 0,1 %A A271976 _Natan Arie Consigli_, Apr 24 2016