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 A184421 #4 Mar 30 2012 18:57:13 %S A184421 1,2,4,5,6,8,9,10,12,13,14,16,17,18,20,21,22,24,25,26,28,29,31,32,33, %T A184421 34,36,37,38,40,41,43,44,45,46,48,49,50,52,53,55,56,57,58,60,61,63,64, %U A184421 65,67,68,69,70,72,73,75,76,77,79,80,81,83,84,85,87,88,89,90,92,93,95,96,97,99,100,101,103,104,105,107,108,109,111,112,114,115,116,117,119,120,121,123,124,125,127,128,129,131,132,133 %N A184421 Lower s-Wythoff sequence, where s=upper Wythoff sequence. Complement of A184422. %C A184421 See A184117 for the definition of lower and upper Wythoff sequences. %t A184421 mex:=First[Complement[Range[1,Max[#1]+1],#1]]&; %t A184421 r=(1+5^(1/2))/2;s[n_]:=Floor[r*n+n];a[1]=1;b[n_]:=b[n]=s[n]+a[n]; %t A184421 a[n_]:=a[n]=mex[Flatten[Table[{a[i],b[i]},{i,1,n-1}]]]; %t A184421 Table[s[n],{n,40}] %t A184421 Table[a[n],{n,100}] %t A184421 Table[b[n],{n,100}] %Y A184421 Cf. A184117, A184422. %K A184421 nonn %O A184421 1,2 %A A184421 _Clark Kimberling_, Jan 13 2011