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 A130526 #2 Mar 30 2012 18:57:10 %S A130526 0,1,-1,2,3,-2,4,-3,5,6,-4,7,8,-5,9,-6,10,11,-7,12,-8,13,14,-9,15,16, %T A130526 -10,17,-11,18,19,-12,20,21,-13,22,-14,23,24,-15,25,-16,26,27,-17,28, %U A130526 29,-18,30,-19,31,32,-20,33,-21,34,35,-22,36,37,-23,38,-24,39,40,-25,41,42,-26 %N A130526 A permutation of the integers induced by the lower and upper Wythoff sequences. %C A130526 Another permutation of the integers is -A130526. %F A130526 a(0) = 0; a(n)=k if n=L(k); a(n)=-k if n=U(k), where L(k) = A000201(k)=Floor(n*phi) = Lower Wythoff sequence, U(k) = A001950(k) = k+L(k) = Upper Wythoff sequence. %e A130526 6=L(4), so a(6)=4. %e A130526 7=U(3), so a(7)=-3. %Y A130526 Cf. A000201, A001950, A026242, A130527. %K A130526 sign %O A130526 0,4 %A A130526 _Clark Kimberling_, Jun 02 2007