A189848 Number of ways to place n nonattacking composite pieces rook + semi-rider[6,6] on an n X n chessboard.

1, 2, 6, 24, 120, 720, 4920, 37488, 319644, 3033264, 31784280, 364902480, 4509620040, 59768680032, 847746532152

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying p(j+6k)-p(j)<>6k for all j>=1, k>=1, j+6k<=n

For information about semi-pieces see semi-bishop (A187235) and semi-queen (A099152).

Links

Table of n, a(n) for n=1..15.

V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)

Wikipedia, Fairy chess piece

Crossrefs

Cf. A189285, A099152, A189843, A189844, A189846, A189847, A189842, A187235

Sequence in context: A177544 A177540 A068201 * A189285 A177545 A177538

Adjacent sequences: A189845 A189846 A189847 * A189849 A189850 A189851

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved