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 A089649 #11 Nov 26 2016 08:07:53
%S A089649 1,2,3,4,6,8,10,13,16,19,23,27,31,37,43,49,57,65,73,83,93,103,116,129,
%T A089649 142,158,174,190,209,228,247,270,293,316,343,370,397,428,459,490,527,
%U A089649 564,601,644,687,730,779,828,877,934,991,1048,1113,1178,1243,1316,1389
%N A089649 a(1)=1, a(2)=2, a(n) = a(n-1) + a(floor((n+1)/3)).
%C A089649 Partial sums of the sequence: a(1)=1, a(1), a(1), a(1), a(2), a(2), a(2), a(3), a(3), ... each term repeated 3 times.
%H A089649 Ivan Neretin, <a href="/A089649/b089649.txt">Table of n, a(n) for n = 1..10000</a>
%t A089649 Fold[Append[#1, #1[[-1]] + #1[[Quotient[#2 + 1, 3]]]] &, {1, 2}, Range[3, 57]] (* _Ivan Neretin_, Nov 25 2016 *)
%o A089649 (PARI) a(n)=if(n<2,1,a(n-1)+a(floor((n+1)/3)))
%Y A089649 Cf. A005704, A089650.
%K A089649 nonn
%O A089649 1,2
%A A089649 _Philippe Deléham_, Jan 02 2004