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 A120135 #22 May 13 2023 19:21:24
%S A120135 5,8,12,18,27,40,60,90,135,203,304,456,684,1026,1539,2309,3463,5195,
%T A120135 7792,11688,17532,26298,39447,59171,88756,133134,199701,299552,449328,
%U A120135 673992,1010988,1516482,2274723,3412084,5118126,7677189,11515784
%N A120135 a(n) = 5 + floor((1 + Sum_{j=1..n-1} a(j)) / 2).
%H A120135 G. C. Greubel, <a href="/A120135/b120135.txt">Table of n, a(n) for n = 1..1000</a>
%F A120135 a(n) ~ c * (3/2)^n, where c = 3.514931952760438754899508881646642282344325354834703833076259269449577... - _Vaclav Kotesovec_, May 07 2023
%t A120135 a[n_]:= a[n]= 5 +Floor[(1+Sum[a[k], {k,n-1}])/2];
%t A120135 Table[a[n], {n,60}] (* _G. C. Greubel_, May 07 2023 *)
%o A120135 (SageMath)
%o A120135 @CachedFunction
%o A120135 def A120135(n): return 5 + (1 + sum(A120135(k) for k in range(1,n)))//2
%o A120135 [A120135(n) for n in range(1,61)] # _G. C. Greubel_, May 07 2023
%Y A120135 Cf. A073941, A072493, A112088, A120134, A120136 - A120209.
%K A120135 nonn
%O A120135 1,1
%A A120135 _Graeme McRae_, Jun 10 2006