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 A190540 #25 Sep 12 2024 15:38:41
%S A190540 0,5,45,335,2385,16775,117585,823415,5764545,40353095,282474225,
%T A190540 1977324695,13841283105,96889002215,678223056465,4747561477175,
%U A190540 33232930504065,232630513856135,1628413597648305,11398895184848855,79792266296563425,558545864081186855,3909821048578793745
%N A190540 a(n) = 7^n - 2^n.
%C A190540 Length-n words from letters {1,2,...,7} with at least one letter >2. [_Joerg Arndt_, Jun 02 2011]
%H A190540 Vincenzo Librandi, <a href="/A190540/b190540.txt">Table of n, a(n) for n = 0..300</a>
%H A190540 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (9,-14).
%F A190540 a(n) = 9*a(n-1) - 14*a(n-2).
%F A190540 G.f.: 5*x/((1-2*x)*(1-7*x)). - _Vincenzo Librandi_, Oct 04 2014
%F A190540 a(n) = 5*A016130(n-1). - _R. J. Mathar_, Mar 10 2022
%F A190540 E.g.f.: exp(2*x)*(exp(5*x) - 1). - _Elmo R. Oliveira_, Sep 10 2024
%t A190540 CoefficientList[Series[5 x/((1 - 2 x) (1 - 7 x)), {x, 0, 30}], x] (* _Vincenzo Librandi_, Oct 04 2014 *)
%o A190540 (Magma) [7^n -2^n: n in [0..30]];
%o A190540 (PARI) a(n)=7^n-1<<n \\ _Charles R Greathouse IV_, Jun 08 2011
%Y A190540 Cf. A016130, A016169, A121213.
%K A190540 nonn,easy
%O A190540 0,2
%A A190540 _Vincenzo Librandi_, Jun 02 2011