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

Author

Vaclav Kotesovec, Dec 06 2011

Keywords

• nonn
• hard

Comments

Fers is a leaper [1,1].

Links

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

Crossrefs

Cf. A201243 - A201248, A002465, A067965.

Formula

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

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