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 A117636 #11 Mar 23 2019 13:35:58 %S A117636 4,8,64,9728,920599396352,780210979034070658749485424425566208 %N A117636 Start with x=4/3; repeatedly apply the map x -> x ceiling(x^2); sequence gives numerators of the resulting sequence of fractions. %C A117636 In this approximate cubing, suggested by T. D. Noe, the 4th iteration yields an integer. Fractions are 4/3, 8/3, 64/3, followed by integers 9728, 920599396352, etc. %H A117636 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. %e A117636 a(2) = 8, the numerator of (4/3) * ceiling ((4/3)^2) = (4/3) * 2 = 8/3. %e A117636 a(3) = 64, the numerator of (8/3) * ceiling ((8/3)^2) = (8/3) * 8 = 64/3. %t A117636 NestList[# Ceiling[#^2]&,4/3,6]//Numerator (* _Harvey P. Dale_, Mar 23 2019 *) %Y A117636 Cf. A072340, A085276, A117596, A117620. %K A117636 easy,frac,nonn %O A117636 1,1 %A A117636 _Jonathan Vos Post_, Apr 08 2006 %E A117636 Data, comments, and examples corrected by _Harvey P. Dale_, Mar 23 2019