login
a(n) = floor( n(n+1)(n+2)(n+3)(n+4) / (n+(n+1)+(n+2)+(n+3)+(n+4)) ).
4

%I #23 Jan 15 2023 09:52:59

%S 0,8,36,100,224,432,756,1232,1900,2808,4004,5544,7488,9900,12852,

%T 16416,20672,25704,31600,38456,46368,55440,65780,77500,90720,105560,

%U 122148,140616,161100,183744,208692,236096,266112,298900,334628,373464,415584

%N a(n) = floor( n(n+1)(n+2)(n+3)(n+4) / (n+(n+1)+(n+2)+(n+3)+(n+4)) ).

%H Vincenzo Librandi, <a href="/A032768/b032768.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1,1,-4,6,-4,1).

%F G.f.: 4*x*(1+x)*(2-x+2*x^2)/((1-x)^5*(1+x+x^2+x^3+x^4)).

%F a(n) = floor( n(n+1)(n+3)(n+4)/5 ). [_Bruno Berselli_, Jun 20 2012]

%t CoefficientList[Series[4*x*(1+x)*(2-x+2*x^2)/((1-x)^5*(1+x+x^2+x^3+x^4)),{x,0,40}],x] (* _Vincenzo Librandi_, Jun 20 2012 *)

%o (Magma) [Floor(n*(n+1)*(n+3)*(n+4)/5): n in [0..36]]; // _Bruno Berselli_, Jun 20 2012

%Y Cf. A032769, A032770.

%K nonn,easy

%O 0,2

%A _Patrick De Geest_, May 15 1998