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A344057
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a(n) = (2*n)! / CatalanNumber(n - 1) for n >= 1 and a(0) = 1.
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2
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1, 2, 24, 360, 8064, 259200, 11404800, 660441600, 48771072000, 4477184409600, 500391198720000, 66920738734080000, 10554356508917760000, 1938789402181632000000, 410402940653807861760000, 99180710658003566592000000, 27141314475238493257728000000
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = 2*n*(2*n-1)*(n-1)!*n! = 2*n^2*(2*n-1)*((n-1)!)^2 for n > 0. a(n) = a(n-1)*n^2*(2*n - 1)/(2*n - 3) for n > 1. - Chai Wah Wu, May 12 2021
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MATHEMATICA
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a[n_] := (2 n)! / CatalanNumber[n - 1]; a[0] := 1; Table[a[n], {n, 0, 16}]
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PROG
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(Python)
from math import factorial
return 1 if n == 0 else 2*n**2*(2*n-1)*factorial(n-1)**2 # Chai Wah Wu, May 12 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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