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 A126431 #29 Sep 07 2024 03:21:53
%S A126431 0,10,200,3000,40000,500000,6000000,70000000,800000000,9000000000,
%T A126431 100000000000,1100000000000,12000000000000,130000000000000,
%U A126431 1400000000000000,15000000000000000,160000000000000000,1700000000000000000,18000000000000000000,190000000000000000000
%N A126431 a(n) = n*10^n.
%H A126431 Vincenzo Librandi, <a href="/A126431/b126431.txt">Table of n, a(n) for n = 0..100</a>
%H A126431 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (20,-100).
%F A126431 a(0)=0, a(1)=10; for n > 1, a(n) = 20*a(n-1) - 100*a(n-2). - _Harvey P. Dale_, Mar 30 2012
%F A126431 G.f.: 10*x/(1 - 10*x)^2. - _Vincenzo Librandi_, Sep 09 2014
%F A126431 From _Amiram Eldar_, Jul 20 2020: (Start)
%F A126431 Sum_{n>=1} 1/a(n) = log(10/9).
%F A126431 Sum_{n>=1} (-1)^(n+1)/a(n) = log(11/10). (End)
%F A126431 From _Elmo R. Oliveira_, Sep 07 2024: (Start)
%F A126431 E.g.f.: 10*x*exp(10*x).
%F A126431 a(n) = n*A011557(n). (End)
%p A126431 A126431 := proc(n) n*10^n ; end proc: # _Bruno Berselli_, Sep 09 2014
%t A126431 Table[n 10^n,{n,0,20}] (* or *) LinearRecurrence[{20,-100},{0,10},20] (* _Harvey P. Dale_, Mar 30 2012 *)
%t A126431 CoefficientList[Series[10 x/(1 - 10 x)^2, {x, 0, 20}], x] (* _Vincenzo Librandi_, Sep 09 2014 *)
%o A126431 (Magma) [n*10^n: n in [0..20]]; // _Vincenzo Librandi_, Sep 09 2014
%o A126431 (PARI) a(n)=n*10^n \\ _Charles R Greathouse IV_, Oct 07 2015
%Y A126431 Cf. A011557.
%K A126431 nonn,easy
%O A126431 0,2
%A A126431 Jonathan R. Love (japanada11(AT)yahoo.ca), Mar 11 2007