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a(n) = 2^(n-3)*(n + 3)*(2*n - 3).
2

%I #26 Aug 16 2024 23:10:52

%S 18,70,224,648,1760,4576,11520,28288,68096,161280,376832,870400,

%T 1990656,4513792,10158080,22708224,50462720,111542272,245366784,

%U 537395200,1172307968,2548039680,5519704064,11920211968,25669140480

%N a(n) = 2^(n-3)*(n + 3)*(2*n - 3).

%H Harry J. Smith, <a href="/A059224/b059224.txt">Table of n, a(n) for n = 3..200</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,8).

%F G.f. = 2x^3*(9-19x+10x^2)/(1-2x)^3. - _Emeric Deutsch_, Jun 27 2009

%F From _G. C. Greubel_, Dec 30 2016: (Start)

%F a(n) = 6*a(n-1) - 12*a(n-2) + 8*a(n-3).

%F E.g.f.: (1/8)*((9 + 8*x - 10*x^2) - (9 - 10*x - 8*x^2)*exp(2*x)). (End)

%p seq(2^(n-3)*(n+3)*(2*n-3), n = 3 .. 32); # _Emeric Deutsch_, Jun 27 2009

%t Table[2^(n-3)*(n + 3)*(2*n - 3), {n,3,50}] (* or *) LinearRecurrence[{6, -12, 8}, {18, 70, 224}, 25] (* _G. C. Greubel_, Dec 30 2016 *)

%o (PARI) { for (n = 3, 200, write("b059224.txt", n, " ", 2^(n - 3)*(n + 3)*(2*n - 3)); ) } \\ _Harry J. Smith_, Jun 25 2009

%Y A diagonal of triangle defined in A059226.

%K nonn,easy

%O 3,1

%A _N. J. A. Sloane_, Jan 19 2001