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 A066319 A labeled structure simultaneously a tree and a cycle. 4
 1, 1, 6, 96, 3000, 155520, 12101040, 1321205760, 192849310080, 36288000000000, 8556520581100800, 2471543044256563200, 858447696200353459200, 353034171594345598156800, 169665960401437500000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 REFERENCES F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 68 (2.1.37). LINKS G. C. Greubel, Table of n, a(n) for n = 1..230 D. E. Knuth, A recurrence related to trees, Proc. Amer. Math. Soc. 105 (1989), 335-349. Reprinted as Chapter 39 of Selected Papers on Discrete Mathematics by D. E. Knuth. Thorsten Weist, On the Euler characteristic of Kronecker moduli spaces, arXiv preprint arXiv:1203.2740 [math.RT], 2012. Cor. 5.3, k=1. But offset 0. FORMULA a(n) = n^(n-2)*(n-1)!. MATHEMATICA Table[n!*n^(n-3), {n, 1, 20}] (* G. C. Greubel, May 29 2019 *) PROG (PARI) a(n) = n^(n-2)*(n-1)!; \\ Michel Marcus, May 29 2019 (Magma) [n^(n-3)*Factorial(n): n in [1..20]]; // G. C. Greubel, May 29 2019 (Sage) [n^(n-3)*factorial(n) for n in (1..20)] # G. C. Greubel, May 29 2019 CROSSREFS Sequence in context: A304646 A251576 A126151 * A186269 A111826 A213797 Adjacent sequences: A066316 A066317 A066318 * A066320 A066321 A066322 KEYWORD nonn AUTHOR Christian G. Bower, Dec 13 2001 EXTENSIONS Knuth reference from David Callan, Feb 07 2004 STATUS approved

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Last modified February 5 18:47 EST 2023. Contains 360087 sequences. (Running on oeis4.)