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 A130527 #2 Mar 30 2012 18:57:10 %S A130527 0,1,2,-1,3,4,-2,5,6,7,-3,8,9,-4,10,11,12,-5,13,14,-6,15,16,-7,17,18, %T A130527 19,-8,20,21,-9,22,23,24,-10,25,26,-11,27,28,-12,29,30,31,-13,32,33, %U A130527 -14,34,35,36,-15,37,38,-16,39,40,41,-17,42,43,-18,44,45,-19,46,47,48 %N A130527 A permutation of the integers induced by the Beatty sequence for sqrt(2). %C A130527 Another permutation of the integers is -A130527. %F A130527 a(0)=0; a(n)=k if n=L(k); a(n)=-k if n=U(k), where L(k) = A001951(k) = Floor(k*sqrt(2)), U(k) = A001952(k) = 2k+L(k). %e A130527 5=L(4), so a(5)=4. %e A130527 6=U(2), so a(6)=-2. %Y A130527 Cf. A001951, A001952, A130526. %K A130527 sign %O A130527 0,3 %A A130527 _Clark Kimberling_, Jun 02 2007