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 A120139 #12 May 14 2023 12:37:41
%S A120139 11,17,25,38,57,85,128,192,288,432,648,972,1458,2187,3280,4920,7380,
%T A120139 11070,16605,24908,37362,56043,84064,126096,189144,283716,425574,
%U A120139 638361,957542,1436313,2154469,3231704,4847556,7271334,10907001,16360501
%N A120139 a(n) = 11 + floor( (1 + Sum_{j=1..n-1} a(j)) / 2).
%H A120139 G. C. Greubel, <a href="/A120139/b120139.txt">Table of n, a(n) for n = 1..1000</a>
%t A120139 a[n_]:= a[n]= 11 +Quotient[1 + Sum[a[k], {k,n-1}], 2];
%t A120139 Table[a[n], {n,60}] (* _G. C. Greubel_, May 08 2023 *)
%o A120139 (SageMath)
%o A120139 @CachedFunction
%o A120139 def A120139(n): return 11 +(1 +sum(A120139(k) for k in range(1,n)))//2
%o A120139 [A120139(n) for n in range(1,60)] # _G. C. Greubel_, May 08 2023
%Y A120139 Cf. A073941, A072493, A112088, A120134 - A120138, A120140 - A120209.
%K A120139 nonn
%O A120139 1,1
%A A120139 _Graeme McRae_, Jun 10 2006