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%I #10 Oct 26 2019 14:30:10
%S 1,1,21,3136,2000376,4032758016,21047953604832,246803372284575744,
%T 5848571832825267643383,258055182353934343170048256,
%U 19860857243854539712080765166683,2528286565488663166137820705009434624
%N a(n) = C(n, 5)^(n-6).
%C 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 5-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
%H Saverio Caminiti and Emanuele G. Fusco, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL10/Caminiti/caminiti.html">On the Number of Labeled k-arch Graphs</a>, Journal of Integer Sequences, Vol 10 (2007), Article 07.7.5.
%H C. Lamathe, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL7/Lamathe/lamathe2.html">The number of labeled k-arch graphs</a>, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.1.
%H B. Leclerc, <a href="https://doi.org/10.4000/msh.2858">Graphes d'arches</a>, Math. Sci. Hum. 157 (2002), 27-48.
%p with(combinat); seq( binomial(n,5)^(n-6), n=5..19 );
%Y Cf. A098721, A098722, A098723
%K easy,nonn
%O 5,3
%A Cedric Lamathe (lamathe(AT)loria.fr), Sep 30 2004