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A092238 Number of ways to write the permutation n,n-1,...,1 of 1,2,...,n as a product of n(n-1)/2 transpositions, where each transposition of 1,2,...,n occurs exactly once. 0
1, 1, 1, 2, 64, 59712, 3580519776 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

If we impose the additional condition on the product t_1 t_2 ... of transpositions that the number of inversions increases by one each time we multiply by a t_i, then the number of ways is given by A005118.

LINKS

Table of n, a(n) for n=0..6.

EXAMPLE

a(3)=2 because 321 = (1,2)(1,3)(2,3) = (2,3)(1,3)(1,2).

CROSSREFS

Cf. A005118.

Sequence in context: A085535 A060613 A139772 * A228252 A339305 A337651

Adjacent sequences:  A092235 A092236 A092237 * A092239 A092240 A092241

KEYWORD

more,nonn

AUTHOR

Richard Stanley, Feb 19 2004

EXTENSIONS

a(0)=1 prepended and a(6) added by Alois P. Heinz, Jul 12 2017

STATUS

approved

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Last modified February 25 12:53 EST 2021. Contains 341607 sequences. (Running on oeis4.)