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 A120138 #15 May 14 2023 12:37:31
%S A120138 10,15,22,33,50,75,112,168,252,378,567,851,1276,1914,2871,4307,6460,
%T A120138 9690,14535,21803,32704,49056,73584,110376,165564,248346,372519,
%U A120138 558779,838168,1257252,1885878,2828817,4243226,6364839,9547258,14320887
%N A120138 a(n) = 10 + floor(Sum_{j=1..n-1} a(j) / 2).
%H A120138 G. C. Greubel, <a href="/A120138/b120138.txt">Table of n, a(n) for n = 1..1000</a>
%t A120138 a[n_]:= a[n]= 10 +Quotient[Sum[a[k], {k,n-1}],2];
%t A120138 Table[a[n], {n,60}] (* _G. C. Greubel_, May 08 2023 *)
%o A120138 (SageMath)
%o A120138 @CachedFunction
%o A120138 def A120138(n): return 10 +sum(A120138(k) for k in range(1,n))//2
%o A120138 [A120138(n) for n in range(1,60)] # _G. C. Greubel_, May 08 2023
%Y A120138 Cf. A073941, A072493, A112088, A120134 - A120137, A120139 - A120209.
%K A120138 nonn
%O A120138 1,1
%A A120138 _Graeme McRae_, Jun 10 2006