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 A022428 #6 Mar 29 2017 20:28:41
%S A022428 1,2,4,9,12,14,17,19,23,26,29,33,36,39,42,45,47,51,53,57,59,62,65,67,
%T A022428 71,73,77,79,83,85,89,92,95,98,101,104,107,110,113,116,119,123,125,
%U A022428 129,132,135
%N A022428 a(n) = c(n-1) + c(n-3) where c is the sequence of numbers not in a.
%H A022428 Ivan Neretin, <a href="/A022428/b022428.txt">Table of n, a(n) for n = 0..10000</a>
%t A022428 Fold[Append[#1, Plus @@ Complement[Range[Max@#1 + 3], #1][[{#2, #2 + 2}]]] &, {1, 2, 4}, Range[43]] (* _Ivan Neretin_, Mar 29 2017 *)
%Y A022428 Cf. A022424 and references therein.
%K A022428 nonn
%O A022428 0,2
%A A022428 _Clark Kimberling_