%I M2776
%S 0,3,9,21,39,66,102,150,210,285,375,483,609,756,924,1116,1332,1575,
%T 1845,2145,2475,2838,3234,3666,4134,4641,5187,5775,6405,7080,7800,
%U 8568,9384,10251,11169,12141,13167,14250,15390
%N Floor(n*(n+2)*(2*n1)/8).
%D From a problem on p. 151 of J. Rec. Math., 7 (1975).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%F a(n) = 3*A002623(n) for n>0.  _M. F. Hasler_, Sep 15 2009
%F G.f.: 3*x/((x+1)*(x1)^4) [Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009]
%F a(1)=0, a(2)=3, a(3)=9, a(4)=21, a(5)=39, a(n)=3*a(n1)2*a(n2) 2*a(n3)+ 3*a(n4)a (n5).  _Harvey P. Dale_, Oct 06 2014
%t Table[Floor[(n(n+2)(2n1))/8],{n,50}] (* or *) LinearRecurrence[{3,2,2,3,1},{0,3,9,21,39},40] (* _Harvey P. Dale_, Oct 06 2014 *)
%o (PARI) vector(50, n, n*(n+2)*(2*n1)\8) \\ _Michel Marcus_, Oct 12 2014
%Y Column 4 of triangle A094953.
%K nonn,easy
%O 1,2
%A _N. J. A. Sloane_, _Robert G. Wilson v_
%E Offset corrected by _Harvey P. Dale_, Oct 06 2014
