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A284417
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Triangular array read by rows. T(n,k) is the number of rooted labeled trees on n nodes with exactly k vertices whose unique descendent is a leaf, n >= 1, 0 <= k <= floor((n-1)/2) + delta_{2,n}.
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0
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1, 0, 2, 3, 6, 16, 48, 145, 420, 60, 1536, 4800, 1440, 19579, 65730, 31500, 840, 290816, 1053696, 698880, 53760, 4942305, 19332936, 16367400, 2388960, 15120, 94689280, 399052800, 410296320, 93542400, 2419200, 2020278931, 9146127870, 11044008360, 3526261200, 200415600, 332640, 47523053568, 230339788800, 319018106880, 133013422080, 12986265600, 127733760
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OFFSET
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1,3
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COMMENTS
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LINKS
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FORMULA
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E.g.f. satisfies: A(x,y) = x exp(A(x,y)) - x^2 + y x^2.
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EXAMPLE
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Triangle begins
1,
0, 2,
3, 6,
16, 48,
145, 420, 60,
1536, 4800, 1440,
19579, 65730, 31500, 840,
290816, 1053696, 698880, 53760,
...
T(3,1)=6 because there are 6 labeled rooted trees (paths) o-o-o and these 6 trees have 1 vertex whose only descendent is a leaf. T(3,0) = 3 because there are 3 labeled trees of the form
o
/ \
o o
and these 3 trees have no such vertices.
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MATHEMATICA
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nn = 10; Range[0, nn]! CoefficientList[Series[-z^2 + u z^2 - ProductLog[-E^((-1 + u) z^2) z], {z, 0, nn}], {z, u}] // Grid
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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