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 A343255 #8 Jun 07 2021 14:54:52 %S A343255 0,1,2,4,256,3126,46662,823551,134217728,3486784402,100000000010, %T A343255 3138428376733,115909305827328,4240251492291543,166680102383370254, %U A343255 7006302246093750016 %N A343255 a(n) is obtained by replacing 2's by n's in the hereditary base-2 expansion of n. %C A343255 The next term, a(16), has 22212093154093428530 digits, and is too large to include. %H A343255 Wikipedia, <a href="https://en.wikipedia.org/wiki/Goodstein's_theorem#Hereditary_base-n_notation">Hereditary base-n notation</a> %F A343255 a(n) = A342707(n, n). %e A343255 For n = 5: %e A343255 - 5 = 2^2^2^0 + 2^0, %e A343255 - so a(5) = 5^5^5^0 + 5^0 = 3126. %Y A343255 Cf. A054382, A342707. %K A343255 nonn %O A343255 0,3 %A A343255 _Rémy Sigrist_, Jun 04 2021