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 A179783 #20 Mar 04 2023 15:33:35
%S A179783 1,3,17,39,81,139,225,335,481,659,881,1143,1457,1819,2241,2719,3265,
%T A179783 3875,4561,5319,6161,7083,8097,9199,10401,11699,13105,14615,16241,
%U A179783 17979,19841,21823,23937,26179,28561,31079
%N A179783 a(n) = 2*n*(n+1)*(n+2)/3 + (-1)^n.
%C A179783 First differences in 2*A081352.
%C A179783 Second differences in 4*A004442.
%H A179783 B. Berselli, <a href="/A179783/b179783.txt">Table of n, a(n) for n = 0..10000</a>.
%H A179783 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,-2,3,-1).
%F A179783 G.f.: (1+10*x^2-4*x^3+x^4)/((1+x)*(1-x)^4); exp(-x)+(2/3)*exp(x)*x*(6+6*x+x^2).
%F A179783 a(n) = 3*a(n-1)-2*a(n-2)-2*a(n-3)+3*a(n-4)-a(n-5) for n>4.
%F A179783 a(n) = 4*A000292(n)+(-1)^n.
%t A179783 LinearRecurrence[{3,-2,-2,3,-1},{1,3,17,39,81},40] (* _Harvey P. Dale_, Mar 04 2023 *)
%o A179783 (Magma) [(2/3)*n*(n+1)*(n+2)+(-1)^n: n in [0..35]];
%o A179783 (PARI) for(n=0, 35, print1((2/3)*n*(n+1)*(n+2)+(-1)^n", "));
%Y A179783 Cf. A005744, A026035, A175109, A131941.
%K A179783 nonn,easy
%O A179783 0,2
%A A179783 _Bruno Berselli_, Jul 29 2010 - Sep 07 2010