A067950 a(n) = number of 3-times (but not 4-times) reformable permutation of {1,...,n}.

1, 0, 1, 8, 31, 56, 219, 605, 2485, 9697, 40571

Offset

6,4

References

A. M. Bersani, "Reformed permutations in Mousetrap and its generalizations", preprint MeMoMat n. 15/2005.

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.

Links

Table of n, a(n) for n=6..16.

A. M. Bersani, On the game Mousetrap.

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

Example

a(6)=1, 165342->132564->125346->136524.

Crossrefs

Cf. A007709, A007711, A007712, A055459.

Sequence in context: A304130 A305479 A302306 * A303037 A230386 A022273

Adjacent sequences: A067947 A067948 A067949 * A067951 A067952 A067953

Keyword

more,nonn

Author

Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Mar 06 2002

Extensions

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