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 A063945 #21 Dec 01 2024 10:04:12
%S A063945 10,90,900,9000,90000,900000,9000000,90000000,900000000,9000000000,
%T A063945 90000000000,900000000000,9000000000000,90000000000000,
%U A063945 900000000000000,9000000000000000,90000000000000000,900000000000000000,9000000000000000000,90000000000000000000
%N A063945 Number of nonnegative integers with n digits.
%C A063945 Also, first differences of A000533. - _Omar E. Pol_, Feb 24 2011
%H A063945 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (10).
%F A063945 a(1) = 10, a(2) = 90, a(n) = a(n-1)*10 for n>2.
%F A063945 a(n) = A052268(n), n>1. - _R. J. Mathar_, Oct 02 2008
%F A063945 From _Stefano Spezia_, Dec 01 2024: (Start)
%F A063945 G.f.: 10*x*(1 - x)/(1 - 10*x).
%F A063945 E.g.f.: (9*exp(10*x) - 9 + 10*x)/10. (End)
%p A063945 a:= n-> `if`(n=1, 10, 9*10^(n-1)):
%p A063945 seq(a(n), n=1..30); # _Alois P. Heinz_, Sep 12 2012
%t A063945 Join[{10},NestList[10#&,90,20]] (* _Harvey P. Dale_, Dec 31 2022 *)
%Y A063945 Column k=1 of A216653.
%K A063945 base,easy,nonn
%O A063945 1,1
%A A063945 _Shyam Sunder Gupta_, Sep 01 2001