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 A132308 #37 Mar 05 2022 01:01:58
%S A132308 1,4,15,50,157,480,1451,4366,13113,39356,118087,354282,1062869,
%T A132308 3188632,9565923,28697798,86093425,258280308,774840959,2324522914,
%U A132308 6973568781,20920706384,62762119195,188286357630,564859072937,1694577218860
%N A132308 a(n) = 2*3^n - n - 1.
%C A132308 Row sums of triangle A132307.
%H A132308 Vincenzo Librandi, <a href="/A132308/b132308.txt">Table of n, a(n) for n = 0..1000</a>
%H A132308 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (5,-7,3).
%F A132308 Binomial transform of A077552.
%F A132308 a(n) = 2*3^n - n - 1. - _Rolf Pleisch_, Sep 26 2010
%F A132308 G.f.: (1-x+2*x^2)/((1-3*x)*(1-x)^2). - _Bruno Berselli_, Mar 31 2011
%e A132308 a(2) = 15 = sum of row 2 terms of triangle A132307: (7 + 7 + 1).
%e A132308 a(2) = 15 = (1, 2, 1) dot (1, 3, 8) = (1 + 6 + 8); where A077552 = (1, 3, 8, 16, 32, 64, ...).
%p A132308 A132308:=n->2*3^n-n-1; seq(A132308(n), n=0..30); # _Wesley Ivan Hurt_, Mar 26 2014
%t A132308 s=1;lst={s};Do[s+=(n+=s++)+n;AppendTo[lst, s], {n, 0, 5!, 1}];lst (* _Vladimir Joseph Stephan Orlovsky_, Nov 15 2008 *)
%t A132308 Table[2*3^n-n-1,{n,0,30}] (* or *) LinearRecurrence[{5,-7,3},{1,4,15},30] (* _Harvey P. Dale_, Aug 06 2013 *)
%t A132308 CoefficientList[Series[(1 - x + 2 x^2)/((1 - 3 x) (1 - x)^2), {x, 0, 50}], x] (* _Vincenzo Librandi_, Mar 27 2014 *)
%Y A132308 Cf. A132307, A132309, A077552.
%K A132308 nonn
%O A132308 0,2
%A A132308 _Gary W. Adamson_, Aug 18 2007
%E A132308 More terms from _Vladimir Joseph Stephan Orlovsky_, Nov 15 2008
%E A132308 Wrong formula 2*n^3-n-1 removed by _Rolf Pleisch_, Oct 19 2010
%E A132308 Simpler definition from _Wesley Ivan Hurt_, Mar 26 2014