OFFSET
1,2
EXAMPLE
90 is in the sequence because for a&b = 3&5, 6! 10!/(3! 5! 8!) = 90.
MATHEMATICA
Flatten[Table[((2i)!(2j)!)/(i! j! (i+j)!), {i, 0, 10}, {j, 0, 10}]]//Union (* Harvey P. Dale, May 31 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Mar 19 2002
STATUS
approved