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 A094797 #21 Oct 03 2023 14:07:54
%S A094797 1,2,21,301,4001,50001,600001,7000001,80000001,900000001,10000000001,
%T A094797 110000000001,1200000000001,13000000000001,140000000000001,
%U A094797 1500000000000001,16000000000000001,170000000000000001,1800000000000000001,19000000000000000001
%N A094797 Number of times 1 is used in writing out all numbers 1 through 10^n.
%H A094797 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (21,-120,100).
%F A094797 a(n) = n*10^(n-1) + 1.
%F A094797 a(n) = 21*a(n-1)-120*a(n-2)+100*a(n-3). - _Colin Barker_, May 23 2014
%F A094797 G.f.: -(99*x^2-19*x+1) / ((x-1)*(10*x-1)^2). - _Colin Barker_, May 23 2014
%F A094797 a(n) = A094798(A011557(n)). - _Michel Marcus_, Oct 03 2023
%t A094797 Table[ n*10^(n - 1) + 1, {n, 0, 17}] (* _Robert G. Wilson v_, Jun 15 2004 *)
%t A094797 LinearRecurrence[{21,-120,100},{1,2,21},20] (* _Harvey P. Dale_, Sep 07 2022 *)
%o A094797 (PARI) Vec(-(99*x^2-19*x+1)/((x-1)*(10*x-1)^2) + O(x^100)) \\ _Colin Barker_, May 23 2014
%Y A094797 Cf. A072290, A078427.
%Y A094797 Cf. A011557, A094798.
%K A094797 base,nonn,easy
%O A094797 0,2
%A A094797 _Lekraj Beedassy_, Jun 11 2004
%E A094797 More terms from _Robert G. Wilson v_, Jun 15 2004
%E A094797 Further terms from _Colin Barker_, May 23 2014