A189846 Number of ways to place n nonattacking composite pieces rook + semi-rider[4,4] on an n X n chessboard.

1, 2, 6, 24, 114, 628, 4062, 30360, 251658, 2308648, 23351268, 259031232, 3091784268, 39697601392, 546982720164, 8064677125440

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying p(j+4k)-p(j)<>4k for all j>=1, k>=1, j+4k<=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. A189283, A099152, A189843, A189844, A189840, A187235

Sequence in context: A324133 A171448 A068199 * A189283 A177522 A216717

Adjacent sequences: A189843 A189844 A189845 * A189847 A189848 A189849

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved