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A255638
Number of n-node rooted trees with a forbidden limb of length 8.
2
1, 1, 2, 4, 9, 20, 48, 115, 285, 717, 1837, 4753, 12451, 32878, 87549, 234654, 632814, 1715446, 4672544, 12780511, 35091842, 96684570, 267223650, 740691451, 2058470490, 5734620428, 16011730686, 44799543203, 125587727914, 352696990890, 992169406959
OFFSET
1,3
COMMENTS
Any rootward 8-node path starting at a leaf contains the root or a branching node.
LINKS
FORMULA
a(n) ~ c * d^n / n^(3/2), where d = 2.95534758805897943282870965508636011438518881375... and c = 0.43969195292137654501555629074396535899093... . - Vaclav Kotesovec, Feb 28 2016
MAPLE
with(numtheory):
g:= proc(n, k) option remember; `if`(n=0, 1, add(add(d*(g(d-1, k)-
`if`(d=k, 1, 0)), d=divisors(j))*g(n-j, k), j=1..n)/n)
end:
a:= n-> g(n-1, 8):
seq(a(n), n=1..40);
CROSSREFS
Column k=8 of A255636.
Sequence in context: A182378 A318801 A318854 * A215971 A034825 A145546
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 28 2015
STATUS
approved