A172148 Number of subsets S of {1,2,3,...,n} with the property that if x is a member of S then at least one of x/2 and 2x is also a member of S.

1, 2, 2, 4, 4, 8, 8, 14, 14, 28, 28, 56, 56, 112, 112, 192, 192, 384, 384, 768, 768, 1536, 1536, 2688, 2688, 5376, 5376, 10752, 10752, 21504, 21504, 37632, 37632, 75264, 75264, 150528, 150528, 301056, 301056, 526848, 526848, 1053696, 1053696, 2107392, 2107392

Offset

1,2

Comments

For the terms a(1) through a(25) is it seen that if n is odd then a(n)=a(n-1); also that if n is not a multiple of 4 then a(2n)=2a(2n-2). Does this behavior continue?

Links

David A. Corneth, Table of n, a(n) for n = 1..6993 (terms < 10^1000)

Crossrefs

Cf. A172020.

Sequence in context: A206558 A385635 A145810 * A205478 A262966 A034397

Adjacent sequences: A172145 A172146 A172147 * A172149 A172150 A172151

Keyword

nonn

Author

John W. Layman, Jan 26 2010

Extensions

a(26)-a(45) from Fausto A. C. Cariboni, Oct 03 2020

Status

approved