A327469 Number of nonempty subsets of [1..n] which are geometric progressions of length >= 3 with rational ratio and are locally maximal.

0, 0, 0, 1, 1, 1, 1, 1, 3, 3, 3, 4, 4, 4, 4, 5, 5, 7, 7, 8, 8, 8, 8, 8, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 19, 19, 19, 19, 19, 19, 19, 19, 20, 22, 22, 22, 23, 29, 33, 33, 34, 34, 34, 34, 34, 34, 34, 34, 35, 35, 35, 37, 40, 40, 40, 40, 41, 41, 41, 41, 45, 45, 45, 49, 50, 50, 50, 50, 51, 55, 55, 55, 56, 56, 56, 56, 56, 56, 58, 58, 59, 59, 59, 59, 60, 60, 66, 68, 77

Offset

1,9

Comments

Exceptionally, DATA section give first 100 terms.

One might have expected that the GP would be required to have an integer ratio, but in fact we allow rational ratios. The GPs can be assumed to be increasing.

Links

Table of n, a(n) for n=1..100.

Crossrefs

Cf. A309095, A327466.

Sequence in context: A134849 A096056 A050501 * A105590 A220845 A361469

Adjacent sequences: A327466 A327467 A327468 * A327470 A327471 A327472

Keyword

nonn

Author

N. J. A. Sloane, Oct 03 2019, using data computed by Rob Pratt.

Status

approved