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a(n) = (n+1)*(5*n^2+4*n+1).
2

%I #10 Jun 10 2016 00:30:05

%S 1,20,87,232,485,876,1435,2192,3177,4420,5951,7800,9997,12572,15555,

%T 18976,22865,27252,32167,37640,43701,50380,57707,65712,74425,83876,

%U 94095,105112,116957,129660,143251

%N a(n) = (n+1)*(5*n^2+4*n+1).

%F From _Chai Wah Wu_, Jun 10 2016: (Start)

%F a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n > 3.

%F G.f.: (13*x^2 + 16*x + 1)/(x - 1)^4. (End)

%Y Cf. A260260 (comment). [_Bruno Berselli_, Jul 22 2015]

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_.