|
Search: id:A088342
|
|
|
| A088342 |
|
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)). |
|
+0
1
|
|
| 1, 3, 14, 93, 837, 9742, 140449, 2420297, 48506250, 1107465929, 28354713349, 804166591614, 25016362993529, 846770894729841, 30978110173770106, 1217913727100939785, 51206137142679936933, 2292551430448659630790, 108888041255668778897857, 5468436908124359403377993
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
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
|
|
CROSSREFS
|
Sequence in context: A101220 A078456 A089462 this_sequence A074531 A091906 A094369
Adjacent sequences: A088339 A088340 A088341 this_sequence A088343 A088344 A088345
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
njas, Nov 13 2003
|
|
|
Search completed in 0.002 seconds
|
