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 A053623 Number of distinct non-extendable sequences {x(1),x(2),...,x(k)} such that each x(i) is in {1,2,...,n} and x(j) AND x(i)<>x(j) for i=2,..k, j=1,..,i-1. 1
 1, 2, 4, 14, 38, 126, 252, 1662, 7180, 39430, 111064, 803876, 2863992, 12123360, 24246720, 329012784 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Related to Mathematical Recreations, Scientific American, March 2000. LINKS EXAMPLE a(3)=4, since the allowable sequences are {1,2}, {2,1}, {3,1,2}, {3,2,1}. ({1,3} is not allowed because 1 AND 3 = 01 AND 11 (base 2) = 1 and {3,1} is not allowed because it can be extended to {3,1,2}.) CROSSREFS Cf. A054668. Sequence in context: A216630 A006611 A007462 * A035010 A055540 A006252 Adjacent sequences:  A053620 A053621 A053622 * A053624 A053625 A053626 KEYWORD nonn AUTHOR John W. Layman, Mar 21 2000 STATUS approved

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Last modified October 17 02:04 EDT 2019. Contains 328106 sequences. (Running on oeis4.)