A172020 -id:A172020 - cp's OEIS frontend

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

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John W. Layman, Jan 26 2010

nonn

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?

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

Cf. A172020.

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

cp's OEIS Frontend

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.

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