A007712 - OEIS

A007712

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

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

(list; graph; refs; listen; history; text; internal format)

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 Erdős is Eighty. Bolyai Society Math. Studies, Vol. 1, pp. 193-206, 1993.

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].

R. K. Guy and R. J. Nowakowski, Mousetrap Amer. Math. Monthly, 101 (1994), 1007-1010.

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 A340909

Adjacent sequences: A007709 A007710 A007711 * A007713 A007714 A007715

KEYWORD

nonn,nice,more

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