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Search: id:A079486
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| A079486 |
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Number of different solutions to a variant of the 3-ball tennis ball problem. |
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+0
3
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| 3, 15, 103, 879, 8787, 99061, 1227369, 16409937, 233588249, 3504149013, 54963273921, 895797910129
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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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.
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REFERENCES
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Larger numbers computed by Matt Richey.
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FORMULA
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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.
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CROSSREFS
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Cf. A000108, A001764, A002293, A049235.
Adjacent sequences: A079483 A079484 A079485 this_sequence A079487 A079488 A079489
Sequence in context: A109777 A135903 A123184 this_sequence A001274 A139766 A003276
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KEYWORD
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nonn
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AUTHOR
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Barry Cipra (bcipra(AT)rconnect.com), Jan 19 2003
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