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 A131874 #36 Mar 04 2022 01:26:57 %S A131874 1,12,30,55,87,126,172,225,285,352,426,507,595,690,792,901,1017,1140, %T A131874 1270,1407,1551,1702,1860,2025,2197,2376,2562,2755,2955,3162,3376, %U A131874 3597,3825,4060,4302,4551,4807,5070,5340,5617,5901,6192,6490,6795,7107,7426 %N A131874 a(n) = (7*n^2 + 15*n + 2) / 2. %C A131874 Row sums of triangle A131873. %H A131874 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1). %F A131874 Binomial transform of (1, 11, 7, 0, 0, 0, ...). %F A131874 a(n) = a(n-1) + 7*n + 4, (with a(0)=1). - _Vincenzo Librandi_, Nov 23 2010 %F A131874 a(n) = (2 + 15*n + 7*n^2)/2; %F A131874 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); %F A131874 G.f.: (1 + 9*x - 3*x^2)/ (1-x)^3. - _Colin Barker_, Sep 13 2012 %e A131874 a(2) = 30 = sum of row 2 terms of triangle A131873: (15 + 8 + 7). %e A131874 a(2) = 30 = (1, 2, 1) dot (1, 11, 7) = (1 + 22 + 7). %p A131874 A131874:=n->(2+15*n+7*n^2)/2; seq(A131874(n), n=0..100); # _Wesley Ivan Hurt_, Mar 26 2014 %o A131874 (PARI) a(n)=(7*n^2+15*n+2)/2 \\ _Charles R Greathouse IV_, Jun 16 2017 %Y A131874 Cf. A131873. %K A131874 nonn,easy %O A131874 0,2 %A A131874 _Gary W. Adamson_, Jul 22 2007 %E A131874 More terms from _Vladimir Joseph Stephan Orlovsky_, Dec 04 2008