A189847 Number of ways to place n nonattacking composite pieces rook + semi-rider[5,5] on an n X n chessboard.

1, 2, 6, 24, 120, 696, 4572, 34260, 290328, 2751480, 28426056, 318900264, 3874868280, 50813711808, 716309557440, 10721493269568

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying p(j+5k)-p(j)<>5k for all j>=1, k>=1, j+5k<=n

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

Links

Table of n, a(n) for n=1..16.

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

Wikipedia, Fairy chess piece

Crossrefs

Cf. A189284, A099152, A189843, A189844, A189846, A189841, A187235

Sequence in context: A177528 A177527 A068200 * A189284 A274970 A177525

Adjacent sequences: A189844 A189845 A189846 * A189848 A189849 A189850

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved