1048509

Appears in sequences

• Number of 2n-bead balanced binary necklaces of fundamental period 2n, equivalent to reversed complement; also Dirichlet convolution of b_n=2^(n-1) with mu(n); also number of components of Mandelbrot set corresponding to Julia sets with an attractive n-cycle.at n=20A000740
• Number of Barlow packings with group P63/mmc(S) that repeat after 4n layers.at n=20A011946
• Number of 2n-bead balanced binary necklaces of fundamental period 2n which are equivalent to their reverse, complement and reversed complement.at n=42A045683
• Number of primitive (aperiodic) word structures of length n which contain exactly two different symbols.at n=20A056278
• Duplicate of A011946.at n=20A195095
• a(n) = Sum_{d|n, gcd(d, n/d) = 1} (-1)^omega(n/d) * 2^(d-1).at n=20A343440
• a(n) = A269795(n)/2.at n=20A365162
• Number of subsets of {1..n} that contain n but do not form a finite arithmetic progression.at n=21A389921