A018931 - OEIS

A018931

The number of permutations of n cards in which 2 is the first card hit and 3 the next hit after 2.

0, 1, 2, 12, 72, 480, 3600, 30240, 282240, 2903040, 32659200, 399168000, 5269017600, 74724249600, 1133317785600, 18307441152000, 313841848320000, 5690998849536000, 108840352997376000, 2189611807358976000, 46225138155356160000, 1021818843434188800000

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OFFSET

3,3

COMMENTS

From the game of Mousetrap.

REFERENCES

Daniel J. Mundfrom, A problem in permutations: the game of "Mousetrap". European J. Combin. 15 (1994), no. 6, 555-560.

LINKS

Table of n, a(n) for n=3..24.

D. J. Mundfrom, A problem of permutations: the Game of "Mousetrap", Eur. J. Combinat. 15 (1994) 555-560, Table 1.

FORMULA

a(n) = A062119(n-3), n > 4. - R. J. Mathar, Oct 02 2008

CROSSREFS

Cf. A002468.

Sequence in context: A322276 A279154 A167747 * A062119 A375607 A181966

Adjacent sequences: A018928 A018929 A018930 * A018932 A018933 A018934

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Offset changed to 3 and more precise definition provided by R. J. Mathar, Oct 02 2008

STATUS

approved