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 A120507 #15 Jul 13 2025 14:01:51
%S A120507 1,2,3,4,4,5,6,7,8,8,9,10,11,12,12,13,14,15,16,16,16,17,18,19,20,20,
%T A120507 21,22,23,24,24,25,26,27,28,28,29,30,31,32,32,32,33,34,35,36,36,37,38,
%U A120507 39,40,40,41,42,43,44,44,45,46,47
%N A120507 Generalized meta-Fibonacci sequence a(n) with parameters s=0 and k=4.
%H A120507 C. Deugau and F. Ruskey, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL12/Ruskey/ruskey6.pdf">Complete k-ary Trees and Generalized Meta-Fibonacci Sequences</a>, J. Integer Seq., Vol. 12. [This is a later version than that in the GenMetaFib.html link]
%H A120507 C. Deugau and F. Ruskey, <a href="http://www.cs.uvic.ca/~ruskey/Publications/MetaFib/GenMetaFib.html">Complete k-ary Trees and Generalized Meta-Fibonacci Sequences</a>
%F A120507 If n=1, a(n)=1. If 2 <= n <= 4, then a(n)=n. If n>4 then a(n)=a(n-a(n-1)) + a(n-1-a(n-2)) + a(n-2-a(n-3)) + a(n-3-a(n-4)).
%F A120507 G.f.: (z / (1 - z)) * Product_{i>=1} (1 - z^(4 * [i])) / (1 - z^[i]), where [i] = (4^i - 1) / 3.
%p A120507 A120507 := proc(n)
%p A120507 option remember;
%p A120507 if n <= 4 then return n end if;
%p A120507 return add(procname(n - i + 1 - procname(n - i)), i = 1 .. 4)
%p A120507 end proc:
%p A120507 seq(A120507(n),n=1..70) ;
%Y A120507 Cf. A120518, A120529.
%K A120507 nonn
%O A120507 1,2
%A A120507 _Frank Ruskey_ and Chris Deugau (deugaucj(AT)uvic.ca), Jun 20 2006