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 A120144 #7 May 14 2023 12:37:40
%S A120144 19,28,42,63,95,142,213,320,480,720,1080,1620,2430,3645,5467,8201,
%T A120144 12301,18452,27678,41517,62275,93413,140119,210179,315268,472902,
%U A120144 709353,1064030,1596045,2394067,3591101,5386651,8079977,12119965,18179948
%N A120144 a(n) = 19 + floor( Sum_{j=1..n-1} a(j) / 2 ).
%H A120144 G. C. Greubel, <a href="/A120144/b120144.txt">Table of n, a(n) for n = 1..1000</a>
%t A120144 a[n_]:= a[n]= 19 +Quotient[Sum[a[k], {k,n-1}], 2];
%t A120144 Table[a[n], {n,60}] (* _G. C. Greubel_, May 14 2023 *)
%o A120144 (SageMath)
%o A120144 @CachedFunction
%o A120144 def A120144(n): return 19 + sum(A120144(k) for k in range(1,n))//2
%o A120144 [A120144(n) for n in range(1,61)] # _G. C. Greubel_, May 14 2023
%Y A120144 Cf. A073941, A072493, A112088, A120134 - A120143, A120145 - A120209.
%K A120144 nonn
%O A120144 1,1
%A A120144 _Graeme McRae_, Jun 10 2006