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 A231684 #16 Dec 09 2021 11:15:31
%S A231684 0,1,3,6,10,15,21,28,36,37,39,42,46,51,57,64,72,81,83,86,90,95,101,
%T A231684 108,116,125,135,138,142,147,153,160,168,177,187,198,202,207,213,220,
%U A231684 228,237,247,258,270,275,281,288,296,305,315,326,338,351,357,364,372,381,391,402,414,427,441,448,456,465,475,486,498,511,525,540,548,557,567,578,590,603,617,632
%N A231684 a(n) = Sum_{i=0..n} digsum_9(i), where digsum_9(i) = A053830(i).
%D A231684 Jean-Paul Allouche and Jeffrey Shallit, Automatic sequences, Cambridge University Press, 2003, p. 94.
%H A231684 Amiram Eldar, <a href="/A231684/b231684.txt">Table of n, a(n) for n = 0..10000</a>
%H A231684 Jean Coquet, <a href="https://doi.org/10.1016/0022-314X(86)90067-3">Power sums of digital sums</a>, J. Number Theory, Vol. 22, No. 2 (1986), pp. 161-176.
%H A231684 P. J. Grabner, P. Kirschenhofer, H. Prodinger and R. F. Tichy, <a href="http://math.sun.ac.za/~hproding/abstract/abs_80.htm">On the moments of the sum-of-digits function</a>, <a href="http://math.sun.ac.za/~hproding/pdffiles/st_andrews.pdf">PDF</a>, Applications of Fibonacci numbers, Vol. 5 (St. Andrews, 1992), pp. 263-271, Kluwer Acad. Publ., Dordrecht, 1993.
%H A231684 Hsien-Kuei Hwang, Svante Janson and Tsung-Hsi 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, Vol. 13, No. 4 (2017), Article #47; <a href="https://www.researchgate.net/profile/Hsien-Kuei-Hwang/publication/320642171_Exact_and_Asymptotic_Solutions_of_a_Divide-and-Conquer_Recurrence_Dividing_at_Half_Theory_and_Applications/links/59f9a5be0f7e9b553ec0eaad">ResearchGate link</a>; <a href="http://140.109.74.92/hk/wp-content/files/2016/12/aat-hhrr-1.pdf">preprint</a>, 2016.
%H A231684 J.-L. Mauclaire and Leo Murata, <a href="https://dx.doi.org/10.3792/pjaa.59.274">On q-additive functions. I</a>, Proc. Japan Acad. Ser. A Math. Sci., Vol. 59, No. 6 (1983), pp. 274-276.
%H A231684 J.-L. Mauclaire and Leo Murata, <a href="https://dx.doi.org/10.3792/pjaa.59.441">On q-additive functions. II</a>, Proc. Japan Acad. Ser. A Math. Sci., Vol. 59, No. 9 (1983), pp. 441-444.
%H A231684 J. R. Trollope, <a href="http://www.jstor.org/stable/2687954">An explicit expression for binary digital sums</a>, Math. Mag., Vol. 41, No. 1 (1968), pp. 21-25.
%F A231684 a(n) ~ 2*n*log(n)/log(3). - _Amiram Eldar_, Dec 09 2021
%t A231684 a[n_] := Plus @@ IntegerDigits[n, 9]; Accumulate @ Array[a, 80, 0] (* _Amiram Eldar_, Dec 09 2021 *)
%o A231684 (PARI) a(n) = sum(i=0, n, sumdigits(i, 9)); \\ _Michel Marcus_, Sep 20 2017
%Y A231684 Cf. A053830, A231685, A231686, A231687.
%K A231684 nonn,base
%O A231684 0,3
%A A231684 _N. J. A. Sloane_, Nov 13 2013