A056174 - OEIS

A056174

Number of non-monotone maps from 1,...,n to 1,...,n.

0, 0, 0, 10, 190, 2878, 45738, 820118, 16764354, 387371878, 9999815254, 285310965190, 8916097744112, 302875096191666, 11112006785441430, 437893890225741870, 18446744073108471242, 827240261884003157974, 39346408075287462440142, 1978419655660278243860198

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OFFSET

0,4

LINKS

Table of n, a(n) for n=0..19.

FORMULA

a(n) = n^n - C(2n, n) + n = A000312(n) - A045992(n)

EXAMPLE

a(3)=10 since the mappings of (1,2,3) to (1,2,1), (1,3,1), (1,3,2), (2,1,2), (2,1,3), (2,3,1), (2,3,2), (3,1,2), (3,1,3) and (3,2,3) all reverse direction

CROSSREFS

Cf. A000312, A000984, A001700, A045992.

Sequence in context: A006409 A173813 A249643 * A033714 A169959 A131521

Adjacent sequences: A056171 A056172 A056173 * A056175 A056176 A056177

KEYWORD

nonn

AUTHOR

Henry Bottomley, Jul 27 2000

EXTENSIONS

More terms from Sean A. Irvine, Apr 15 2022

STATUS

approved