A074986 Number of nonempty subsets of {1,2,3,...,n} that are closed under both GCD and LCM.

1, 3, 5, 9, 11, 18, 20, 28, 32, 39, 41, 62, 64, 71, 78, 94, 96, 117, 119, 140, 147, 154, 156, 214, 218, 225, 233, 254, 256, 301, 303, 335, 342, 349, 356, 440, 442, 449, 456, 514, 516, 561, 563, 584, 605, 612, 614, 766, 770, 791, 798, 819, 821, 879, 886, 944, 951

Offset

1,2

Comments

I.e. number of division lattices with values from 1 to n. - Franklin T. Adams-Watters, Sep 21 2006

Links

Table of n, a(n) for n=1..57.

Crossrefs

Cf. A051839, A122977, A122978.

Sequence in context: A270836 A100456 A059819 * A307435 A123328 A226175

Adjacent sequences: A074983 A074984 A074985 * A074987 A074988 A074989

Keyword

nonn

Author

John W. Layman, Oct 02 2002

Extensions

More terms from Franklin T. Adams-Watters, Sep 21 2006

Status

approved