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a(n) = (2n)!/(n!*a(n-2)), with a(0) = 1, a(1) = 1.
2

%I #11 Jul 15 2024 23:33:28

%S 1,1,12,120,140,252,4752,68640,109200,257040,6139584,109549440,

%T 210974400,591192000,16576876800,343108846080,758663942400,

%U 2419157664000,76585170816000,1777303822694400,4379008275532800,15472932418944000,540078624594432000,13756331587654656000

%N a(n) = (2n)!/(n!*a(n-2)), with a(0) = 1, a(1) = 1.

%t a[0] = 1; a[1] = 1;

%t a[n_] := a[n] = (2n)!/(n!*a[n - 2]);

%t Table[a[n], {n, 0, 20}]

%Y Cf. A372986, A372987.

%K nonn

%O 0,3

%A _Clark Kimberling_, Jul 09 2024