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 A067691 #8 Feb 05 2021 03:51:33 %S A067691 0,1,2,9,1000,1004006004001, %T A067691 1020191144865623440455270145683555422808365843606721760320032 %N A067691 a(n) = (a(n-1) + 1)^(n-1) for n > 0, a(0) = 0. %C A067691 a(7) has 361 digits. %e A067691 Given a(3) = 9: a(4) = (a(4-1)+1)^(4-1) = (9+1)^3 = 1000. %o A067691 (PARI) a(n) = if (n==0, 0, (a(n-1) + 1)^(n-1)); \\ _Michel Marcus_, Feb 05 2021 %Y A067691 Cf. A004019. %K A067691 nonn %O A067691 0,3 %A A067691 _Reinhard Zumkeller_, Feb 04 2002