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A007712
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Number of once reformable permutations of {1,2,...,n}.
(Formerly M1283)
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5
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1, 2, 4, 14, 72, 316, 1730, 9728, 64330, 444890, 3645441, 28758111, 265434293, 2522822881, 25717118338
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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REFERENCES
| A. M. Bersani, "Reformed permutations in Mousetrap and its generalizations", preprint MeMoMat, No. 15, 2005.
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.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| A. M. Bersani, On the game Mousetrap.
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EXAMPLE
| For n=3, 123,312,231,213 are unreformed but 132->123, 321->213 so a(3)=2
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CROSSREFS
| Cf. A007709, A007711, A055459, A067950.
Sequence in context: A055790 A020131 A032147 * A192815 A075098 A052856
Adjacent sequences: A007709 A007710 A007711 * A007713 A007714 A007715
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| 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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