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 A130031 #17 Mar 31 2025 11:39:13
%S A130031 1,1,-1,5,-55,1045,-30305,1242505,-68337775,4851982025,-431826400225,
%T A130031 47069077624525,-6166049168812775,955737621165980125,
%U A130031 -172988509431042402625,36154598471087862148625,-8640949034589999053521375,2341697188373889743504292625
%N A130031 Row sums of triangle A129467.
%C A130031 See the M. Bruschi et al. reference given in A129467.
%H A130031 G. C. Greubel, <a href="/A130031/b130031.txt">Table of n, a(n) for n = 0..250</a>
%F A130031 a(n) = Sum_{j=0..n} A129467(n,j), n >= 0.
%F A130031 a(n) = Sum_{j=0..n-1} A130559(n, j), n>= 1.
%F A130031 From _Vaclav Kotesovec_, Aug 24 2016: (Start)
%F A130031 a(n) = (-1)^n*Product_{k=1..n} (k^2 - k - 1).
%F A130031 a(n) ~ 2*(-1)^n * cos(sqrt(5)*Pi/2) * n^(2*n) / exp(2*n). (End)
%F A130031 a(n) + (n^2-n-1)*a(n-1) = 0. - _R. J. Mathar_, Jan 21 2018
%t A130031 Table[(-1)^n*Product[k^2-k-1, {k, 1, n}], {n, 0, 20}] (* _Vaclav Kotesovec_, Aug 24 2016 *)
%t A130031 Table[FullSimplify[(-1)^n * Cos[Sqrt[5]*Pi/2] * Gamma[n+(Sqrt[5]+1)/2] * Gamma[n-(Sqrt[5]-1)/2]/Pi], {n, 0, 20}] (* _Vaclav Kotesovec_, Aug 24 2016 *)
%o A130031 (Magma) [1] cat [n le 1 select 1 else -(n^2-n-1)*Self(n-1): n in [1..30]]; // _G. C. Greubel_, Feb 10 2024
%o A130031 (SageMath)
%o A130031 def A130031(n): return 1 if n<2 else -(n^2-n-1)*A130031(n-1)
%o A130031 [A130031(n) for n in range(31)] # _G. C. Greubel_, Feb 10 2024
%Y A130031 Cf. A129467, A130559.
%K A130031 sign,easy
%O A130031 0,4
%A A130031 _Wolfdieter Lang_, May 04 2007