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 A198964 #26 Aug 15 2024 12:13:52
%S A198964 3,31,283,2551,22963,206671,1860043,16740391,150663523,1355971711,
%T A198964 12203745403,109833708631,988503377683,8896530399151,80068773592363,
%U A198964 720618962331271,6485570660981443,58370135948832991,525331223539496923
%N A198964 a(n) = (7*9^n - 1)/2.
%H A198964 Vincenzo Librandi, <a href="/A198964/b198964.txt">Table of n, a(n) for n = 0..1000</a>
%H A198964 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>,signature (10,-9).
%F A198964 a(n) = 9*a(n-1)+4.
%F A198964 a(n) = 10*a(n-1)-9*a(n-2), n>1.
%F A198964 G.f.: (3 + x)/(1 - 10*x + 9*x^2). - _Vincenzo Librandi_, Jan 03 2013
%F A198964 From _Elmo R. Oliveira_, Aug 15 2024: (Start)
%F A198964 E.g.f.: exp(x)*(7*exp(8*x) - 1)/2.
%F A198964 a(n) = A198965(n)/2. (End)
%t A198964 CoefficientList[Series[(3 + x)/(1 - 10 x + 9 x^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Jan 03 2013 *)
%t A198964 LinearRecurrence[{10,-9},{3,31},30] (* _Harvey P. Dale_, Oct 10 2017 *)
%o A198964 (Magma) [(7*9^n-1)/2: n in [0..20]];
%o A198964 (PARI) a(n)=7*9^n\2 \\ _Charles R Greathouse IV_, Oct 16 2015
%Y A198964 Cf. A198965.
%K A198964 nonn,easy
%O A198964 0,1
%A A198964 _Vincenzo Librandi_, Nov 01 2011