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A079486
Number of different solutions to a variant of the 3-ball tennis ball problem.
2
3, 15, 103, 879, 8787, 99061, 1227369, 16409937, 233588249, 3504149013, 54963273921, 895797910129
OFFSET
1,1
COMMENTS
You're given labeled balls three at time (labeled 1,2,3 then 4,5,6 etc.), choose two balls from those still on hand (including the three you've just been given) and throw the larger out the window onto the front lawn, the smaller onto the back lawn.
REFERENCES
Larger numbers computed by Matt Richey.
FORMULA
a(n) is the number of 2 X n matrices of positive integers, with the numbers in each row and column increasing, the numbers in column k less than or equal to 3k and no number used more than once.
CROSSREFS
KEYWORD
nonn
AUTHOR
Barry Cipra, Jan 19 2003
STATUS
approved