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A206477
(Number of permutations of {1,2,...,n} for which sums of three consecutive numbers (with wraparound) are all distinct)/2n
0
3, 3, 36, 76, 690, 2996, 22368, 147472, 1284653, 11006509
OFFSET
4,1
COMMENTS
Essentially different ways 1,2,...,n can be placed around a circle so that sums of three consecutive numbers are distinct.
EXAMPLE
a(4)=3 because up to rotation/reflection the only three permutations which work are 1234, 1243, and 1324
CROSSREFS
Sequence in context: A368387 A213281 A303820 * A372022 A219210 A218863
KEYWORD
hard,nonn
AUTHOR
Steve Butler, Feb 08 2012
STATUS
approved