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 A049960 #19 Sep 26 2019 01:55:14
%S A049960 1,2,4,8,19,35,73,161,376,680,1363,2741,5536,11375,23737,51647,121495,
%T A049960 219254,438511,877037,1754128,3508559,7018105,14040383,28098967,
%U A049960 56295692,112908400,227132417,459528811,940138484,1965086401,4276793213,10059144016,18153201632,36306403267
%N A049960 a(n) = a(1) + a(2) + ... + a(n-1) + a(m) for n >= 3, where m = 2*n - 3 - 2^(p+1) and p is the unique integer such that 2^p < n-1 <= 2^(p+1), with a(1) = 1 and a(2) = 2.
%F A049960 a(n) = a(A006257(n-2)) + Sum_{i = 1..n-1} a(i) for n >= 3 with a(1) = 1 and a(2) = 2. - _Petros Hadjicostas_, Sep 24 2019
%p A049960 a := proc(n) option remember; if n<3 then return [1,2][n] fi; add(a(i), i=1..n-1) + a(2*(n-2) - Bits:-Iff(n-2, n-2)) end: seq(a(n), n=1..37); # _Petros Hadjicostas_, Sep 24 2019 by modifying a program by _Peter Luschny_
%Y A049960 Cf. A006257, A049939, A049940, A049964.
%K A049960 nonn
%O A049960 1,2
%A A049960 _Clark Kimberling_
%E A049960 Name edited and more terms from _Petros Hadjicostas_, Sep 24 2019