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Search: id:A007712
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| A007712 |
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Number of once reformable permutations of {1,2,...,n}.
(Formerly M1283)
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+0
6
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| 1, 2, 4, 14, 72, 316, 1730, 9728, 64330, 444890, 3645441, 28758111, 265434293, 2522822881, 25717118338
(list; graph; listen)
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OFFSET
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2,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. K. Guy, Unsolved Problems Number Theory, Section E37.
R. K. Guy and R. J. Nowakowski, ``Mousetrap,'' in D. Miklos, V.T. Sos and T. Szonyi, eds., Combinatorics, Paul Erdos is Eighty. Bolyai Society Math. Studies, Vol. 1, pp. 193-206, 1993.
R. K. Guy and R. J. Nowakowski, ``Mousetrap,'' Amer. Math. Monthly, 101 (1994), 1007-1010.
A. M. Bersani, "Reformed permutations in Mousetrap and its generalizations", preprint MeMoMat, No. 15, 2005.
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LINKS
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A. M. Bersani, On the game Mousetrap.
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EXAMPLE
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For n=3, 123,312,231,213 are unreformed but 132->123, 321->213 so a(3)=2
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CROSSREFS
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Cf. A007709, A007711, A055459, A067950.
Sequence in context: A055790 A020131 A032147 this_sequence A075098 A052856 A093462
Adjacent sequences: A007709 A007710 A007711 this_sequence A007713 A007714 A007715
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Mar 06 2002
2 more terms from Alberto M. Bersani (bersani(AT)dmmm.uniroma1.it), Feb 07 2007
One more term from Alberto M. Bersani (bersani(AT)dmmm.uniroma1.it), Feb 24 2008
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