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A339838
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Number of rooted bicolored trees on n unlabeled nodes such that black nodes are not adjacent to each other and every white node is adjacent to a black node.
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4
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1, 2, 4, 10, 27, 75, 221, 662, 2042, 6402, 20407, 65828, 214720, 706600, 2343767, 7826752, 26293468, 88796471, 301290197, 1026595232, 3511246069, 12050780294, 41488523002, 143246116231, 495881545520, 1720771421470, 5984652387281, 20857113949868, 72829214554641, 254762923125929
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OFFSET
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1,2
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LINKS
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PROG
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(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}
seq(n)={my(u=v=w=[]); for(n=1, n, my(t1=EulerT(v), t2=EulerT(u+v)); u=concat([1], EulerT(v+w)); v=concat([0], t2-t1); w=concat([1], t1)); u+v}
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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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