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A092081
Triangle of certain double factorials.
1
1, 1, 2, 1, 3, 8, 1, 4, 15, 48, 1, 5, 24, 105, 384, 1, 6, 35, 192, 945, 3840, 1, 7, 48, 315, 1920, 10395, 46080, 1, 8, 63, 480, 3465, 23040, 135135, 645120, 1, 9, 80, 693, 5760, 45045, 322560, 2027025, 10321920, 1, 10, 99, 960, 9009, 80640, 675675, 5160960
OFFSET
0,3
COMMENTS
This is the rectangular array A(3;m,n) := (2*n+m)!!/m!!, m >= 0, n >= 0, read by SW-NE diagonals. For n!! see A006882 (double factorials).
FORMULA
a(m, n)=(n+m)!!/(m-n)!!, 0<=n<=m, else 0, with 0!! := 1.
CROSSREFS
Diagonals give: A000165 (double factorials of 2*n), A001147(n+1), A002866, A051577-83.
Columns give: A000012 (powers of 1), A000027 (naturals >=2), A005563, 3*A077415, for n=0..3.
Sequence in context: A298096 A053190 A135299 * A203997 A057740 A320875
KEYWORD
nonn,easy,tabl
AUTHOR
Wolfdieter Lang, Mar 19 2004
STATUS
approved