This site is supported by donations to The OEIS Foundation.



Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A007518 Floor(n*(n+2)*(2*n-1)/8).
(Formerly M2776)

%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*n-1)/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)*(x-1)^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(n-1)-2*a(n-2)- 2*a(n-3)+ 3*a(n-4)-a (n-5). - _Harvey P. Dale_, Oct 06 2014

%t Table[Floor[(n(n+2)(2n-1))/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*n-1)\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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 22 06:27 EST 2014. Contains 252328 sequences.