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 A139577 #24 Nov 29 2024 20:19:42
%S A139577 0,13,30,51,76,105,138,175,216,261,310,363,420,481,546,615,688,765,
%T A139577 846,931,1020,1113,1210,1311,1416,1525,1638,1755,1876,2001,2130,2263,
%U A139577 2400,2541,2686,2835,2988,3145,3306,3471,3640,3813,3990
%N A139577 a(n) = n*(2*n + 11).
%H A139577 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A139577 a(n) = 2*n^2 + 11*n.
%F A139577 a(n) = a(n-1) + 4*n + 9 (with a(0)=0). - _Vincenzo Librandi_, Nov 24 2010
%F A139577 From _Elmo R. Oliveira_, Nov 29 2024: (Start)
%F A139577 G.f.: x*(13 - 9*x)/(1-x)^3.
%F A139577 E.g.f.: exp(x)*x*(13 + 2*x).
%F A139577 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)
%t A139577 s=0;lst={s};Do[s+=n++ +13;AppendTo[lst, s], {n, 0, 7!, 4}];lst (* _Vladimir Joseph Stephan Orlovsky_, Nov 19 2008 *)
%t A139577 Table[n(2n+11),{n,0,50}] (* or *) LinearRecurrence[{3,-3,1},{0,13,30},50] (* _Harvey P. Dale_, Mar 17 2019 *)
%o A139577 (PARI) a(n)=n*(2*n+11) \\ _Charles R Greathouse IV_, Jun 17 2017
%Y A139577 Cf. A014105, A014106, A033537, A130861, A139576, A139578, A139579, A139580, A139581.
%K A139577 easy,nonn
%O A139577 0,2
%A A139577 _Omar E. Pol_, May 19 2008