

A007712


Number of once reformable permutations of {1,2,...,n}.
(Formerly M1283)


5



1, 2, 4, 14, 72, 316, 1730, 9728, 64330, 444890, 3645441, 28758111, 265434293, 2522822881, 25717118338
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OFFSET

2,2


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 ErdÅ‘s is Eighty. Bolyai Society Math. Studies, Vol. 1, pp. 193206, 1993.
R. K. Guy and R. J. Nowakowski, "Mousetrap," Amer. Math. Monthly, 101 (1994), 10071010.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=2..16.
A. M. Bersani, On the game Mousetrap.
R. K. Guy and R. J. Nowakowski, Mousetrap, Preprint, Feb 10 1993 [Annotated scanned copy]


EXAMPLE

For n=3, 123, 312, 231, 213 are unreformed but 132>123, 321>213 so a(3)=2.


CROSSREFS

Cf. A007709, A007711, A055459, A067950.
Sequence in context: A020131 A261002 A032147 * A192815 A075098 A052856
Adjacent sequences: A007709 A007710 A007711 * A007713 A007714 A007715


KEYWORD

nonn,nice


AUTHOR

N. J. A. Sloane


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


STATUS

approved



