A201861 Number of ways to place n nonattacking ferses on an n X n board.

1, 4, 38, 661, 16286, 527654, 21191208, 1015335608, 56484795166, 3576188894116, 253756155257774, 19937566770720487, 1717714713900798962, 160977153444563000938, 16300053518916522372836, 1773133639291617644092637, 206197950879511078156507433

Offset

1,2

Comments

Fers is a leaper [1,1].

Links

Table of n, a(n) for n=1..17.

V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 423.

Formula

Asymptotic (Kotesovec, 2011): a(n) ~ n^(2n)/n!*exp(-5/2).

Crossrefs

Cf. A201243 - A201248, A002465, A067965.

Sequence in context: A138562 A354686 A177382 * A171779 A171203 A096332

Adjacent sequences: A201858 A201859 A201860 * A201862 A201863 A201864

Keyword

nonn,hard

Author

Vaclav Kotesovec, Dec 06 2011

Extensions

a(15) from Vaclav Kotesovec, Jan 03 2012

a(16) from Vaclav Kotesovec, Aug 31 2016

a(17) from Vaclav Kotesovec, May 30 2021

Status

approved