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A038094
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Number of rooted graphs on n labeled nodes where the root has degree 2.
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6
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6, 96, 1920, 61440, 3440640, 352321536, 67645734912, 24739011624960, 17416264183971840, 23779006032516218880, 63309225660971181146112, 330036748754793764694786048, 3379576307249088150474609131520
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OFFSET
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3,1
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 3..80
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FORMULA
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a(n) = n * binomial(n-1, 2) * 2^binomial(n-1, 2).
a(n) = n * A103904(n-1) for n >= 3. - Andrew Howroyd, Nov 23 2020
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MATHEMATICA
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Table[n*Binomial[n-1, 2]*2^Binomial[n-1, 2], {n, 3, 20}] (* Vaclav Kotesovec, Mar 29 2014 *)
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PROG
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(Magma) [n*Binomial(n-1, 2)*2^Binomial(n-1, 2): n in [3..20]]; // Vincenzo Librandi, Mar 29 2014
(PARI) a(n) = {n * binomial(n-1, 2) * 2^binomial(n-1, 2)} \\ Andrew Howroyd, Nov 23 2020
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CROSSREFS
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Cf. A006125, A038095, A038096, A038097, A103904.
Sequence in context: A001805 A139743 A156460 * A346184 A304646 A251576
Adjacent sequences: A038091 A038092 A038093 * A038095 A038096 A038097
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KEYWORD
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nonn,easy
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AUTHOR
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Christian G. Bower, Jan 04 1999
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STATUS
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approved
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