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 A016200 #41 Aug 23 2025 11:49:14
%S A016200 1,9,61,381,2317,13965,83917,503757,3023053,18139341,108838093,
%T A016200 653032653,3918204109,23509241037,141055478989,846332939469,
%U A016200 5077997767885,30467986869453,182807921741005,1096847531494605,6581085191064781,39486511150582989,236919066911886541,1421514401488096461
%N A016200 Expansion of g.f. 1/((1-x)*(1-2*x)*(1-6*x)).
%H A016200 Muniru A Asiru, <a href="/A016200/b016200.txt">Table of n, a(n) for n = 0..250</a>
%H A016200 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-20,12).
%F A016200 a(n) = (9*6^n - 5*2^n + 1)/5. - _Bruno Berselli_, Feb 09 2011
%F A016200 a(0)=1, a(n) = 6*a(n-1) + 2^(n+1) - 1. - _Vincenzo Librandi_, Feb 09 2011
%F A016200 a(n) = Sum_{k=0..n} 2^(n-1-k)*(3^(n+1-k) - 1). - _J. M. Bergot_, Feb 06 2018
%F A016200 From _Elmo R. Oliveira_, Mar 26 2025: (Start)
%F A016200 E.g.f.: exp(x)*(9*exp(5*x) - 5*exp(x) + 1)/5.
%F A016200 a(n) = A016129(n+1) - A003464(n+2) = A241275(n+2)/5.
%F A016200 a(n) = 9*a(n-1) - 20*a(n-2) + 12*a(n-3). (End)
%p A016200 seq((9*6^n-5*2^n+1)/5, n=0..100); # _Muniru A Asiru_, Feb 06 2018
%t A016200 CoefficientList[Series[1/((1-x)(1-2x)(1-6x)),{x,0,30}],x] (* or *) LinearRecurrence[{9,-20,12},{1,9,61},30] (* _Harvey P. Dale_, Aug 23 2025 *)
%o A016200 (GAP) List([0..100],n->(9*6^n-5*2^n+1)/5); # _Muniru A Asiru_, Feb 06 2018
%Y A016200 Cf. A003464, A016129, A241275.
%K A016200 nonn,easy,changed
%O A016200 0,2
%A A016200 _N. J. A. Sloane_