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 A199771 #24 Oct 24 2024 03:50:16
%S A199771 1,5,12,26,45,75,112,164,225,305,396,510,637,791,960,1160,1377,1629,
%T A199771 1900,2210,2541,2915,3312,3756,4225,4745,5292,5894,6525,7215,7936,
%U A199771 8720,9537,10421,11340,12330,13357,14459,15600,16820,18081,19425,20812,22286,23805
%N A199771 Row sums of the triangle in A199332.
%C A199771 a(n) = Sum_{k=1..n} A199332(n,k);
%C A199771 a(2*n-1) = A015237(n); a(2*n) = A048395(n);
%C A199771 a(n+1) = A200252(n).
%H A199771 Reinhard Zumkeller, <a href="/A199771/b199771.txt">Table of n, a(n) for n = 1..1000</a>
%H A199771 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,-4,1,2,-1).
%F A199771 G.f.: x*( 1+3*x+x^2+x^3 ) / ((1+x)^2*(x-1)^4). - _R. J. Mathar_, Nov 24 2011
%F A199771 a(n) = n*(3+2*n^2+4*n+(-1)^n)/8. - _R. J. Mathar_, Jun 23 2023
%t A199771 LinearRecurrence[{2,1,-4,1,2,-1},{1,5,12,26,45,75},50] (* _Harvey P. Dale_, Apr 27 2019 *)
%o A199771 (Haskell)
%o A199771 a199771 = sum . a199332_row
%o A199771 (PARI) a(n)=([0,1,0,0,0,0; 0,0,1,0,0,0; 0,0,0,1,0,0; 0,0,0,0,1,0; 0,0,0,0,0,1; -1,2,1,-4,1,2]^(n-1)*[1;5;12;26;45;75])[1,1] \\ _Charles R Greathouse IV_, Jun 18 2017
%K A199771 nonn,easy
%O A199771 1,2
%A A199771 _Reinhard Zumkeller_, Nov 23 2011