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 A227386 #10 Jul 12 2013 14:19:49
%S A227386 0,0,1,2,2,3,3,3,4,5,5,5,5,6,7,8,8,9,9,9,9,9,10,11,12,13,13,14,14,15,
%T A227386 15,15,16,17,17,17,17,17,17,18,19,20,21,22,22,23,23,24,24,25,25,25,26,
%U A227386 27,27,27,28,29,29,29,29,30,31,32,32,33,33,33,33,33
%N A227386 a(n) = n - 1 - a(a(n-1)) - a(a(a(n-2))) - a(a(a(a(n-3)))) - a(a(a(a(a(n-4))))) - ... with a(0) = 0.
%t A227386 a[n_] := a[n] = Which[n ==0, 0, True, n - 1 - Sum[Nest[a, n - i, i + 1], {i, 1, n}]]; Table[a[n], {n, 0, 100}]
%Y A227386 Cf. A227145.
%K A227386 nonn
%O A227386 0,4
%A A227386 _José María Grau Ribas_, Jul 09 2013