OFFSET
1,2
COMMENTS
Equivalently the number of ways of placing the maximal number of nonattacking black-square queens on an inverted n X n chessboard, that is a board with the a1 square white, the a2 and b1 squares black, etc.
FORMULA
a(2n) = A352325(2n).
PROG
(Python) See A352426.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Martin Ehrenstein, Mar 22 2022
EXTENSIONS
a(21)-a(24) from Vaclav Kotesovec, Mar 23 2022
a(25)-a(26) from Vaclav Kotesovec, Apr 01 2022
STATUS
approved