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 A134230 #20 Apr 05 2025 16:11:06
%S A134230 3,120,10200,1002000,100020000,10000200000,1000002000000,
%T A134230 100000020000000,10000000200000000,1000000002000000000,
%U A134230 100000000020000000000,10000000000200000000000,1000000000002000000000000,100000000000020000000000000,10000000000000200000000000000
%N A134230 a(n) = (10^n+1)^2-1.
%C A134230 Previous name was: -1 + Sum of first 10^n + 1 odd numbers.
%H A134230 Colin Barker, <a href="/A134230/b134230.txt">Table of n, a(n) for n = 0..499</a>
%H A134230 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (110,-1000).
%F A134230 a(n) = (10^n+1)^2-1. - _N. J. A. Sloane_, Oct 15 2007
%F A134230 a(n) = 110*a(n-1)-1000*a(n-2). - _Colin Barker_, Jan 27 2015
%F A134230 G.f.: -3*(70*x-1) / ((10*x-1)*(100*x-1)). - _Colin Barker_, Jan 27 2015
%t A134230 LinearRecurrence[{110,-1000},{3,120},15] (* or *) CoefficientList[Series[-3*(70*x-1) / ((10*x-1)*(100*x-1)),{x,0,14}],x] (* _James C. McMahon_, Apr 05 2025 *)
%o A134230 (PARI) Vec(-3*(70*x-1)/((10*x-1)*(100*x-1)) + O(x^100)) \\ _Colin Barker_, Jan 27 2015
%Y A134230 Cf. A134228, A134229.
%K A134230 easy,nonn
%O A134230 0,1
%A A134230 _Enoch Haga_, Oct 14 2007
%E A134230 Edited by _N. J. A. Sloane_, Oct 15 2007
%E A134230 Offset and name corrected by _Arkadiusz Wesolowski_, Jun 12 2013
%E A134230 New name (using formula by _N. J. A. Sloane_) from _Joerg Arndt_, Jan 27 2015