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 A163261 #11 Mar 05 2019 14:27:26 %S A163261 1,3,18,702,1038258,2292015792222,11135478955084481409955218, %T A163261 263108590829588406010634295716681354685770554450302 %N A163261 Numerators of fractions in the approximation of the square root of 2 by means of: f(n)= 3f(n-1)/(f(n-1)^2+1); with f(1)= 1. %C A163261 For root c: f(n) = (1+c)*f(n-1)/(f(n-1)^2+1). %F A163261 a(n+1) = 3*a(n)*A163262(n). - _Philippe Deléham_, Oct 11 2011 %o A163261 (PARI) f(n) = if (n==1, 1, 3*f(n-1)/(f(n-1)^2+1)); %o A163261 a(n) = numerator(f(n)); \\ _Michel Marcus_, Mar 05 2019 %Y A163261 Cf. A002193 (sqrt(2)), A163262 (denominators). %Y A163261 Cf. A001601 and A051009: Newton's method. %K A163261 nonn,frac %O A163261 1,2 %A A163261 _Mark Dols_, Jul 23 2009 %E A163261 More terms from _Michel Marcus_, Mar 05 2019