OFFSET
0,4
COMMENTS
a(n) = 2^n - A050291(n); a(2*k+1) = a(2*k)*2;
a non-double-free subset contains at least one subset {x,y} with y=2*x.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..3321 (first 401 terms from T. D. Noe)
Steven R. Finch, Triple-Free Sets of Integers [From Steven Finch, Apr 20 2019]
Eric Weisstein's World of Mathematics, Double-Free Set
Reinhard Zumkeller, Illustration of initial terms
MATHEMATICA
A050291[n_] := A050291[n] = If[n == 1, 2, With[{b = IntegerExponent[2n, 2]}, A050291[n - 1] Fibonacci[b + 2]/Fibonacci[b + 1]]];
a[n_] := If[n == 0, 0, 2^n - A050291[n]];
Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Nov 10 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 19 2003
STATUS
approved