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 A067091 #14 Dec 02 2023 23:17:03
%S A067091 2,2,329,4101,4919,5737,6556,7374,8193,9012,9830,10649,11467,12286,
%T A067091 13104,13923,14741,15560,16378,17197,18015,18834,19652,20471,212899,
%U A067091 22108437,2292696195,237454867452,24564011532104,2538253631893694
%N A067091 Floor(X/Y) where X = concatenation of the (n+1)-st even number through the (2n)-th even number and Y = concatenation of first n even numbers.
%H A067091 Hans Havermann, <a href="http://chesswanks.com/seq/a067091">First 1000 terms</a>
%e A067091 a(4) = floor(10121416/2468) = floor(4101.05996758508914100486223662885) = 4101.
%e A067091 a(7) = floor(16182022242628/2468101214) = floor(6556.4662222268166673) = 6556.
%t A067091 z[n_] := Block[{a = "", m = n}, While[ Length[m] > 0, a = StringJoin[a, ToString[m[[1]]]]; m = Drop[m, 1]]; ToExpression[a]]; Table[ Floor[ z[Table[2i, {i, n + 1, 2n}]] / z[ Table[2i, {i, 1, n}]]], {n, 1, 30}]
%Y A067091 Cf. A067088, A067089, A067090.
%K A067091 easy,base,nonn
%O A067091 1,1
%A A067091 _Amarnath Murthy_, Jan 07 2002
%E A067091 Edited by _N. J. A. Sloane_ and _Robert G. Wilson v_, Jun 14 2002