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 A045681 #20 Feb 12 2014 18:15:47 %S A045681 0,1,2,3,4,6,7,8,9,11,12,13,14,16,17,18,19,21,22,23,24,25,26,28,29,30, %T A045681 31,33,34,35,36,38,39,40,41,43,44,45,46,47,48,50,51,52,53,55,56,57,58, %U A045681 60,61,62,63,65,66,67,68,69,70,72,73 %N A045681 Extension of Beatty sequence; complement of A045682. %C A045681 (s,t)-sequences; the case s=2, t=3. %D A045681 Clark Kimberling, Complementary Equations, Journal of Integer Sequences, Vol. 10 (2007), Article 07.1.4. %H A045681 A. S. Fraenkel, <a href="http://arXiv.org/abs/math.CO/9809074">Heap games, numeration systems and sequences</a>, Annals of Combinatorics, 2 (1998), 197-210. %H A045681 <a href="/index/Be#Beatty">Index entries for sequences related to Beatty sequences</a> %F A045681 a(n)=mex {a(i), b(i):0<=i<n}, where b=A045682, mex S=least integer >= 0 not in the sequence S. %t A045681 s=2; t=3; %t A045681 mex:=First[Complement[Range[1,Max[#1]+1],#1]]&; %t A045681 a[0]=0; b[n_]:=b[n]=s*a[n]+t*n; %t A045681 a[n_]:=a[n]=mex[Flatten[Table[{a[i],b[i]},{i,0,n-1}]]]; %t A045681 Table[a[n],{n,200}] (* A045681 *) %t A045681 Table[b[n],{n,200}] (* A045682 *) %t A045681 (* From _Clark Kimberling_, Apr 02 2011 *) %Y A045681 Cf. A045671, A045672. %K A045681 nonn %O A045681 0,3 %A A045681 _Aviezri S. Fraenkel_