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 A064616 #16 Mar 18 2024 09:33:21
%S A064616 9,89,789,6789,56789,456789,3456789,23456789,123456789,123456789,
%T A064616 -9876543211,-209876543211,-3209876543211,-43209876543211,
%U A064616 -543209876543211,-6543209876543211,-76543209876543211,-876543209876543211,-9876543209876543211
%N A064616 a(n) = (10^n-1)*(91/81)-n*10^n/9.
%H A064616 Harry J. Smith, <a href="/A064616/b064616.txt">Table of n, a(n) for n=1..150</a>
%H A064616 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (21,-120,100).
%F A064616 a(n) = a(n-1)+(10-n)*10^(n-1) = (19-n)*A002275(n)-A064617(n) = 10*A002275(n)-A014925(n).
%F A064616 a(n) = 21*a(n-1)-120*a(n-2)+100*a(n-3). G.f.: x*(100*x-9) / ((x-1)*(10*x-1)^2). - _Colin Barker_, Sep 15 2014
%t A064616 LinearRecurrence[{21,-120,100},{9,89,789},20] (* _Harvey P. Dale_, May 15 2022 *)
%o A064616 (PARI) { a=0; q=1; for (n=1, 150, a+=(10 - n)*q; q*=10; write("b064616.txt", n, " ", a) ) } \\ _Harry J. Smith_, Sep 20 2009
%o A064616 (PARI) Vec(x*(100*x-9)/((x-1)*(10*x-1)^2) + O(x^100)) \\ _Colin Barker_, Sep 15 2014
%Y A064616 Cf. A002275, A014925, A064617.
%K A064616 base,easy,sign
%O A064616 1,1
%A A064616 _Henry Bottomley_, Sep 26 2001