OFFSET
1,2
LINKS
Muniru A Asiru, Table of n, a(n) for n = 1..36
FORMULA
a(n) = 2^n * Product_{k=1..n} (2*k-1)!/(k-1)!.
a(n) = 2^n * A086205(n).
From Alois P. Heinz, Jun 30 2022: (Start)
a(n) = Product_{i=1..n-1} Product_{j=i..n-1} (i+j).
a(n) = A112332(n). (End)
MAPLE
seq(mul(mul((j+k), j=1..k), k=1..n-1), n=1..9); # Zerinvary Lajos, Sep 21 2007
PROG
(PARI) a(n)=my(t=1); prod(k=1, n-1, t*=4*k-2) \\ Charles R Greathouse IV, Oct 25 2011
(PARI) a(n)=matdet(matrix(n, n, i, j, pollegendre(i-1, j-1)<<(i-1))) \\ Charles R Greathouse IV, Oct 25 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jul 13 2005
STATUS
approved