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A372987
a(n) = (2*n)!/(n!*a(n-1)), with a(0)=1.
2
1, 2, 6, 20, 84, 360, 1848, 9360, 55440, 318240, 2106720, 13366080, 96909120, 668304000, 5233092480, 38761632000, 324451733760, 2558267712000, 22711621363200, 189311810688000, 1771506466329600, 15523568476416000, 152349556104345600, 1397121162877440000
OFFSET
0,2
FORMULA
a(n) = Product_{k=0..floor((n-1)/2)} 2*(2*n-4*k-1). - Andrew Howroyd, Jul 10 2024
MATHEMATICA
a[0] = 1; a[n_] := a[n] = (2n)!/(n!*a[n - 1]);
Table[a[n], {n, 0, 30}]
PROG
(PARI) a(n)=prod(k=0, (n-1)\2, 2*(2*n-4*k-1)) \\ Andrew Howroyd, Jul 10 2024
CROSSREFS
Sequence in context: A177476 A266600 A177474 * A177480 A365229 A089179
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jul 09 2024
STATUS
approved