524265

Appears in sequences

• Number of n-bead black-white reversible strings with fundamental period n.at n=20A045625
• Number of primitive (aperiodic) reversible strings with n beads using exactly two different colors.at n=19A056318
• a(n) = Sum_{d|n, gcd(d, n/d) = 1} (-1)^omega(n/d) * 2^(d-1).at n=19A343440