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 A097425 #12 Nov 14 2018 09:34:30 %S A097425 500,15500500,1510001505011550050050015500500 %N A097425 a(1) = 500, then a(n) is the concatenation of the roman numerals (I, V, X, L, C, D, M) visible in a(n-1) written in English. %e A097425 a(1) = 500, which is fIVe hunDreD, so a(2) = concat(1, 5, 500, 500) = 15500500, which is fIVeteen MILLIon fIVe hunDreD thousanD fIVe hunDreD, so a(3) = concat(1, 5, 1000, 1, 50, 50, 1, 1, 5, 500, 500, 500, 1, 5, 500, 500), etc. %Y A097425 Cf. A002904, A092302. %K A097425 nonn,word,less %O A097425 1,1 %A A097425 _Pierre CAMI_, Aug 21 2004