OFFSET
1,3
COMMENTS
We discovered that the numbers that appear in the lower left triangle of the ED1 array A167546 (m <= n) behave in a regular way, see the formula below. This rather simple regularity doesn't show up in the upper right triangle of the ED1 array (m > n).
LINKS
G. C. Greubel, Table of n, a(n) for the first 50 rows
FORMULA
a(n,m) = 4^(m-1)*(m-1)!*(n+m-2)!/(2*m-2)!.
EXAMPLE
The first few triangle rows are:
[1]
[1, 4]
[2, 12, 32]
[6, 48, 160, 384]
[24, 240, 960, 2688, 6144]
[120, 1440, 6720, 21504, 55296, 122880]
MAPLE
a := proc(n, m): 4^(m-1)*(m-1)!*(n+m-2)!/(2*m-2)! end: seq(seq(a(n, m), m=1..n), n=1..8); # Johannes W. Meijer, revised Nov 23 2012
MATHEMATICA
Flatten[Table[(4^(m-1) (m-1)!(n+m-2)!)/(2m-2)!, {n, 10}, {m, n}]] (* Harvey P. Dale, Sep 29 2013 *)
CROSSREFS
KEYWORD
AUTHOR
Johannes W. Meijer, Nov 10 2009
STATUS
approved