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%I #13 Oct 02 2023 13:49:07
%S 1,2,6,20,69,242,857,3054,10930,39236,141153,508598,1834641,6623450,
%T 23926334,86468052,312587197,1130277914,4087621545,14784539846,
%U 53478888618,193456813508,699850536281,2531866279710,9159810802849,33139021206962,119894215708662
%N Expansion of (1-x)*(1-2x)*(1-3x)/((1-5x+5*x^2)*(1-3x+x^2)).
%C A diagonal of the square array A217770.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (8, -21, 20, -5).
%F a(n) = A217770(n,n).
%F a(n) = 8*a(n-1) - 21*a(n-2) + 20*a(n-3) -5*a(n-4) for n>=4, a(0) = 1, a(1) = 2, a(2) = 6, a(3) = 20.
%Y Cf. A217770, A217777, A217778, A217779.
%K nonn,easy
%O 0,2
%A _Philippe Deléham_, Mar 24 2013