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 A014993 #31 Aug 04 2024 16:38:02
%S A014993 1,-10,111,-1220,13421,-147630,1623931,-17863240,196495641,
%T A014993 -2161452050,23775972551,-261535698060,2876892678661,-31645819465270,
%U A014993 348104014117971,-3829144155297680,42120585708274481
%N A014993 a(n) = (1 - (-11)^n)/12.
%C A014993 q-integers for q = -11.
%H A014993 Vincenzo Librandi, <a href="/A014993/b014993.txt">Table of n, a(n) for n = 1..900</a>
%H A014993 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-10,11).
%F A014993 a(n) = a(n-1) + q^{(n-1)} = {(q^n - 1) / (q - 1)}.
%F A014993 G.f.: x/((1 - x)*(1 + 11*x)). - _Vincenzo Librandi_, Oct 22 2012
%F A014993 a(n) = -10*a(n-1) + 11*a(n-2). - _Vincenzo Librandi_, Oct 22 2012
%F A014993 E.g.f.: (exp(x) - exp(-11*x))/12. - _G. C. Greubel_, May 26 2018
%p A014993 a:=n->sum ((-11)^j, j=0..n): seq(a(n), n=0..25); # _Zerinvary Lajos_, Dec 16 2008
%t A014993 LinearRecurrence[{-10, 11}, {1, -10}, 40] (* _Vincenzo Librandi_, Oct 22 2012 *)
%o A014993 (Sage) [gaussian_binomial(n,1,-11) for n in range(1,18)] # _Zerinvary Lajos_, May 28 2009
%o A014993 (Magma) I:=[1, -10]; [n le 2 select I[n] else -10*Self(n-1) +11*Self(n-2): n in [1..30]]; // _Vincenzo Librandi_, Oct 22 2012
%o A014993 (PARI) for(n=1,30, print1((1-(-11)^n)/12, ", ")) \\ _G. C. Greubel_, May 26 2018
%Y A014993 Cf. A077925, A014983, A014985, A014986, A014987, A014989, A014990, A014991, A014992, A014994. - _Zerinvary Lajos_, Dec 16 2008
%K A014993 sign,easy
%O A014993 1,2
%A A014993 _Olivier Gérard_
%E A014993 Better name from _Ralf Stephan_, Jul 14 2013