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Search: id:A088342
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| A088342 |
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Let T = Sum_{k >= 1} k^(k-1)*x^k be the g.f. for rooted labeled trees (A000169); sequence has g.f. T/(x(1-T)). |
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| 1, 3, 14, 93, 837, 9742, 140449, 2420297, 48506250, 1107465929, 28354713349, 804166591614, 25016362993529, 846770894729841, 30978110173770106, 1217913727100939785, 51206137142679936933, 2292551430448659630790, 108888041255668778897857, 5468436908124359403377993
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)=number of forests of rooted trees on [n] whose vertex sets partition [n] into intervals of integers, that is, such that if i<j<k and i,k are vertices in the same component tree, then so is j. For example with n=3, a(n)=14 counts all (n+1)^(n-1)=16 rooted forests on [3] except the 2 forests consisting of a rooted tree on vertex set {1,3} and another on vertex set {2}. - David Callan (callan(AT)stat.wisc.edu), Oct 24 2004
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CROSSREFS
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Sequence in context: A101220 A078456 A089462 this_sequence A074531 A091906 A094369
Adjacent sequences: A088339 A088340 A088341 this_sequence A088343 A088344 A088345
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Nov 13 2003
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