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A361244
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Number of noncrossing bridgeless cacti with n nodes.
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2
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1, 1, 0, 1, 1, 6, 13, 57, 169, 673, 2301, 8933, 32747, 127063, 483484, 1889957, 7352241, 29003446, 114481435, 455542880, 1816976042, 7285391071, 29291855748, 118218771203, 478372112363, 1941436590561, 7897802784418, 32205683248225, 131602039333873
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OFFSET
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0,6
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LINKS
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FORMULA
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G.f. 1 + A(x) where A(x) satisfies A(x) = x^2*(x - A(x)^2)/(x^2 - x*A(x)^2 - A(x)^4).
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PROG
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(PARI) seq(n)={my(g=1+O(x)); for(n=1, n\2, g=1/(1 - x^2*g^4/(1 - x*g^2))); Vec(1 + x*g + O(x*x^n))}
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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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