589746

Appears in sequences

• Number of subsets of {1, ..., n} that are double-free or sum-free.at n=23A088813
• a(0)=0, a(1)=1, a(2)=2, a(3)=3, a(4)=12; for n > 4, a(n) = 8*a(n-2) - a(n-4) - 3.at n=15A105045