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n*(1+3*n+6*n^2)/2.
0

%I #6 Mar 30 2012 18:40:36

%S 0,5,31,96,218,415,705,1106,1636,2313,3155,4180,5406,6851,8533,10470,

%T 12680,15181,17991,21128,24610,28455,32681,37306,42348,47825,53755,

%U 60156,67046,74443,82365,90830,99856,109461,119663,130480,141930,154031,166801,180258

%N n*(1+3*n+6*n^2)/2.

%F a(n) = n*(1+3*n+6*n^2)/2. a(n) = n*A085473(n)/2. a(n) = n*[C(2n+3,3)-C(2n,3)]/2. - _Jonathan Vos Post_, Mar 10 2006

%F a(0) = 0, a(1) = 5, a(2) = 31, a>2: a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + 18; G.f. = (5*x+11*x^2+2*x^3)/(1-x)^4 - _Zak Seidov_, Mar 10 2006

%Y Cf. A085473.

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Mar 09 2006