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A189843 Number of ways to place n nonattacking composite pieces rook + semi-rider[2,2] on an n X n chessboard. 4
1, 2, 5, 18, 71, 356, 2097, 14212, 105821, 887576, 8093601, 81310936, 876456695, 10257217440, 127631146697, 1705775408656 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying p(j+2k)-p(j)<>2k for all j>=1, k>=1, j+2k<=n
about semi-pieces see semi-bishop (A187235) and semi-queen (A099152)
LINKS
CROSSREFS
Sequence in context: A365120 A268570 A141494 * A045612 A371494 A103940
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved

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Last modified July 14 20:49 EDT 2024. Contains 374323 sequences. (Running on oeis4.)