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 A099674 #18 Jul 22 2025 17:03:16
%S A099674 0,7,84,861,8638,86415,864192,8641969,86419746,864197523,8641975300,
%T A099674 86419753077,864197530854,8641975308631,86419753086408,
%U A099674 864197530864185,8641975308641962,86419753086419739,864197530864197516,8641975308641975293,86419753086419753070,864197530864197530847
%N A099674 Partial sums of repdigits of A002281.
%H A099674 Harvey P. Dale, <a href="/A099674/b099674.txt">Table of n, a(n) for n = 0..1000</a>
%H A099674 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (12,-21,10).
%F A099674 a(n) = (7/81)*(10^(n+1) - 9*n - 10). - R. Piyo (nagoya314(AT)yahoo.com), Dec 10 2004
%F A099674 From _Elmo R. Oliveira_, Apr 02 2025: (Start)
%F A099674 G.f.: 7*x/((1 - x)^2*(1 - 10*x)).
%F A099674 E.g.f.: 7*exp(x)*(10*exp(9*x) - 9*x - 10)/81.
%F A099674 a(n) = 7*A014824(n).
%F A099674 a(n) = 12*a(n-1) - 21*a(n-2) + 10*a(n-3) for n > 3. (End)
%e A099674 7 + 77 + 777 + 7777 + 77777 = a(5) = 86415.
%t A099674 <<NumberTheory`NumberTheoryFunctions` Table[{k, Table[Apply[Plus, Table[k*(10^n-1)/9, {n, 1, m}]], {m, 1, 35}]}, {k, 1, 9}]
%t A099674 Table[8/9*Sum[10^i - 1, {i, n}], {n, 18}] (* _Robert G. Wilson v_, Nov 20 2004 *)
%t A099674 Accumulate[LinearRecurrence[{11,-10},{0,7},25]] (* _Harvey P. Dale_, Jul 22 2025 *)
%Y A099674 Cf. A002275-A002283, A014824, A057932, A099669-A099675.
%K A099674 base,nonn,easy
%O A099674 0,2
%A A099674 _Labos Elemer_, Nov 17 2004
%E A099674 More terms from _Elmo R. Oliveira_, Apr 02 2025
%E A099674 a(0)=0 prepended by _Harvey P. Dale_, Jul 22 2025