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 A073849 #29 Dec 18 2019 02:06:00
%S A073849 0,1,3,4,5,6,8,10,12,13,14,15,16,17,18,19,20,21,23,25,27,29,31,33,35,
%T A073849 37,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,
%U A073849 61,62,63,64,65,66,68,70,72,74,76,78,80,82,84,86,88,90,92
%N A073849 Cumulative sum of initial digits of (n base 3).
%H A073849 Hsien-Kuei Hwang, S. Janson, T.-H. Tsai, <a href="http://140.109.74.92/hk/wp-content/files/2016/12/aat-hhrr-1.pdf">Exact and asymptotic solutions of the recurrence f(n) = f(floor(n/2)) + f(ceiling(n/2)) + g(n): theory and applications</a>, Preprint 2016.
%H A073849 Hsien-Kuei Hwang, S. Janson, T.-H. Tsai, <a href="https://doi.org/10.1145/3127585">Exact and Asymptotic Solutions of a Divide-and-Conquer Recurrence Dividing at Half: Theory and Applications</a>, ACM Transactions on Algorithms, 13:4 (2017), #47; DOI: 10.1145/3127585.
%F A073849 a(n) = Sum_{i=0..n} A000030(A007089(n)).
%e A073849 n in init cumulative
%e A073849 n base 3 dgt sum
%e A073849 - ------ ---- ----------
%e A073849 0 0 0 0
%e A073849 1 1 1 1
%e A073849 2 2 2 3
%e A073849 3 10 1 4
%e A073849 4 11 1 5
%e A073849 5 12 1 6
%t A073849 Accumulate[Table[First[IntegerDigits[n,3]],{n,0,80}]] (* _Harvey P. Dale_, Mar 24 2015 *)
%o A073849 (PARI) lista(nn) = {s = 0; print1(s, ", "); for (n=1, nn, s += digits(n,3)[1]; print1(s, ", "););} \\ _Michel Marcus_, Mar 24 2015
%Y A073849 Cf. A000030, A007089, A109453.
%K A073849 easy,nonn,base
%O A073849 0,3
%A A073849 _Jonathan Vos Post_, Aug 28 2005
%E A073849 Corrected by _Harvey P. Dale_, Mar 24 2015