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A227806
Number of rooted identity trees with n nodes and exactly 2 subtrees from the root.
3
1, 1, 3, 5, 11, 22, 49, 104, 232, 513, 1159, 2619, 5989, 13734, 31729, 73555, 171377, 400631, 940104, 2212542, 5222932, 12360976, 29327260, 69735757, 166170966, 396727768, 948897250, 2273409345, 5455374972, 13110384631, 31550978034, 76029236983, 183437066950
OFFSET
4,3
LINKS
FORMULA
a(n) ~ c * d^n / n^(3/2), where d = A246169 = 2.51754035263200389079535459846344... and c = 0.14400421547102520752812171064737721... - Vaclav Kotesovec, Jun 07 2021
EXAMPLE
: o : o : o o o :
: / \ : / \ : / \ / \ / \ :
: o o : o o : o o o o o o :
: | : | : | | / \ | :
: o : o : o o o o o :
: : | : | | | :
: : o : o o o :
: : : | :
: n=4 : n=5 : n=6 o :
CROSSREFS
Column k=2 of A227774.
Sequence in context: A005830 A007008 A018110 * A262431 A262085 A015915
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 31 2013
STATUS
approved