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A292212
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Number of (unlabeled) rooted trees with n leaf nodes and without unary nodes or outdegrees larger than six.
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2
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0, 1, 1, 2, 5, 12, 33, 89, 258, 756, 2279, 6957, 21592, 67689, 214451, 684850, 2203384, 7133042, 23222003, 75971636, 249646198, 823597534, 2726859943, 9057797752, 30176758016, 100810029178, 337614951216, 1133292965615, 3812333876764, 12849946139206
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OFFSET
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0,4
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LINKS
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MAPLE
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b:= proc(n, i, v) option remember; `if`(n=0,
`if`(v=0, 1, 0), `if`(i<1 or v<1 or n<v, 0,
`if`(v=n, 1, add(binomial(a(i)+j-1, j)*
b(n-i*j, i-1, v-j), j=0..min(n/i, v)))))
end:
a:= proc(n) option remember; `if`(n<2, n,
add(b(n, n+1-j, j), j=2..min(n, 6)))
end:
seq(a(n), n=0..35);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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