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A007518 [ n(n+2)(2n-1)/8 ].
(Formerly M2776)
1

%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 [ n(n+2)(2n-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 3*A002623(n) for n>0. - M. F. Hasler, Sep 15 2009

%F G.f.:3*x/((x+1)*(x-1)^4) [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009]

%Y Column 4 of triangle A094953.

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_, _Robert G. Wilson v_

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Last modified September 17 19:47 EDT 2014. Contains 246869 sequences.