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 A195574 #11 Mar 11 2014 01:40:39
%S A195574 1,12,651,5720,12480,17549,236588,12758199,112130200,244626200,
%T A195574 343998201,4637596612,250086218851,2197976167920,4795162766680,
%U A195574 6743052715749,90906168553188,4902190049156399,43084728731444400,93994780307828400
%N A195574 Denominators a(n) of Pythagorean approximations b(n)/a(n) to 2/5.
%C A195574 See A195500 for a discussion and references.
%t A195574 r = 2/5; z = 26;
%t A195574 p[{f_, n_}] := (#1[[2]]/#1[[
%t A195574 1]] &)[({2 #1[[1]] #1[[2]], #1[[1]]^2 - #1[[
%t A195574 2]]^2} &)[({Numerator[#1], Denominator[#1]} &)[
%t A195574 Array[FromContinuedFraction[
%t A195574 ContinuedFraction[(#1 + Sqrt[1 + #1^2] &)[f], #1]] &, {n}]]]];
%t A195574 {a, b} = ({Denominator[#1], Numerator[#1]} &)[
%t A195574 p[{r, z}]] (* A195574, A195575 *)
%t A195574 Sqrt[a^2 + b^2] (* A195576 *)
%t A195574 (* _Peter J. C. Moses_, Sep 02 2011 *)
%Y A195574 Cf. A195500, A195575, A195576.
%K A195574 nonn
%O A195574 1,2
%A A195574 _Clark Kimberling_, Sep 21 2011