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, 2, 4, 14, 38, 126, 252, 1662, 7180, 39430, 111064, 803876, 2863992, 12123360, 24246720, 329012784, 2602608516

Offset: 1

Author

John W. Layman, Mar 21 2000

Keywords

• nonn

Examples

			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.
(3,1) is not allowed because it can be extended to (3,1,2).
		

References

• Related to Mathematical Recreations, Scientific American, March 2000.

Links

• Sean A. Irvine, Java program (github)

Crossrefs

Cf. A054668.

Extensions

a(17) from Sean A. Irvine, Jan 04 2022