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 A117596 #9 Nov 18 2013 11:01:01 %S A117596 6,12,36,288,16704,55808064,622908012647232, %T A117596 77602878444025201997703040704, %U A117596 1204441348559630271252918141028336694332989128001036771264,290135792424028156178425357986052529062710984863337179470336908191924417208517059859206222048920739921330978585792 %N A117596 Start with x=6/5; repeatedly apply the map x -> x*ceiling(x); sequence gives numerators of the resulting sequence of fractions. %C A117596 After 18 terms the fractions become integers, the first of which has 57735 digits. %D A117596 N. J. A. Sloane, Seven Staggering Sequences, in Homage to a Pied Puzzler, E. Pegg Jr., A. H. Schoen and T. Rodgers (editors), A. K. Peters, Wellesley, MA, 2009, pp. 93-110. %H A117596 J. C. Lagarias and N. J. A. Sloane, Approximate squaring (<a href="http://neilsloane.com/doc/apsq.pdf">pdf</a>, <a href="http://neilsloane.com/doc/apsq.ps">ps</a>), Experimental Math., 13 (2004), 113-128. %H A117596 N. J. A. Sloane, <a href="http://neilsloane.com/doc/g4g7.pdf">Seven Staggering Sequences</a>. %e A117596 The sequence of fractions begins 6/5, 12/5, 36/5, 288/5, 16704/5, 55808064/5, 622908012647232/5, 77602878444025201997703040704/5, ... The first 17 denominators are 5, the rest are 1. %t A117596 f[x_] := x*Ceiling[x]; NestList[f, 6/5, 9] // Numerator (* _Jean-François Alcover_, Nov 18 2013 *) %Y A117596 Cf. A072340, A085276. %K A117596 nonn,frac %O A117596 1,1 %A A117596 _N. J. A. Sloane_, Apr 07 2006