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A038094 Number of rooted graphs on n labeled nodes where the root has degree 2. 6
6, 96, 1920, 61440, 3440640, 352321536, 67645734912, 24739011624960, 17416264183971840, 23779006032516218880, 63309225660971181146112, 330036748754793764694786048, 3379576307249088150474609131520 (list; graph; refs; listen; history; text; internal format)
OFFSET
3,1
LINKS
FORMULA
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
MATHEMATICA
Table[n*Binomial[n-1, 2]*2^Binomial[n-1, 2], {n, 3, 20}] (* Vaclav Kotesovec, Mar 29 2014 *)
PROG
(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
CROSSREFS
Sequence in context: A139743 A361737 A156460 * A346184 A304646 A251576
KEYWORD
nonn,easy
AUTHOR
Christian G. Bower, Jan 04 1999
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)