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A098721
a(n) = C(n, 2)^(n-3) = (n(n-1)/2)^(n-3).
10
1, 1, 6, 100, 3375, 194481, 17210368, 2176782336, 373669453125, 83733937890625, 23762680013799936, 8335775831236199424, 3543686674874777831491, 1795856326022129150390625, 1069932053790720000000000000
OFFSET
2,3
COMMENTS
There is a flaw in the paper by Lamathe that we point out in our contribution. This sequence does not give the number of labeled 2-arch graphs (here named arch graphs) on n nodes. The correct sequence is given in our paper. - Saverio Caminiti and Emanuele G. Fusco (fusco(AT)di.uniroma1.it), Sep 18 2007
LINKS
Saverio Caminiti and Emanuele G. Fusco, On the Number of Labeled k-arch Graphs, Journal of Integer Sequences, Vol 10 (2007), Article 07.7.5.
C. Lamathe, The number of labeled k-arch graphs, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.1.
B. Leclerc, Graphes d'arches, Math. Sci. Hum. 157 (2002), 27-48.
MAPLE
seq( (n*(n-1)/2)^(n-3), n=2..19 );
MATHEMATICA
Table[Binomial[n, 2]^(n-3), {n, 2, 20}] (* Harvey P. Dale, Jan 25 2012 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cedric Lamathe (lamathe(AT)loria.fr), Sep 30 2004
STATUS
approved