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 A195568 #12 Jun 05 2015 03:19:38
%S A195568 3,8,120,637,2176,30848,164483,561288,7958776,42435837,144810240,
%T A195568 2053333248,10948281603,37360480520,529752019320,2824614217597,
%U A195568 9638859164032,136673967651200,728739519858563,2486788303839624,35261353901990392
%N A195568 Denominators a(n) of Pythagorean approximations b(n)/a(n) to 7/4.
%C A195568 See A195500 for a discussion and references.
%F A195568 Empirical g.f.: x*(3*x^6+8*x^5+120*x^4-134*x^3+120*x^2+8*x+3) / (x^9-257*x^6-257*x^3+1). - _Colin Barker_, Jun 04 2015
%t A195568 r = 7/4; z = 26;
%t A195568 p[{f_, n_}] := (#1[[2]]/#1[[
%t A195568 1]] &)[({2 #1[[1]] #1[[2]], #1[[1]]^2 - #1[[
%t A195568 2]]^2} &)[({Numerator[#1], Denominator[#1]} &)[
%t A195568 Array[FromContinuedFraction[
%t A195568 ContinuedFraction[(#1 + Sqrt[1 + #1^2] &)[f], #1]] &, {n}]]]];
%t A195568 {a, b} = ({Denominator[#1], Numerator[#1]} &)[
%t A195568 p[{r, z}]] (* A195568, A195569 *)
%t A195568 Sqrt[a^2 + b^2] (* A195570 *)
%t A195568 (* _Peter J. C. Moses_, Sep 02 2011 *)
%Y A195568 Cf. A195500, A195569, A195570.
%K A195568 nonn
%O A195568 1,1
%A A195568 _Clark Kimberling_, Sep 21 2011