A305594 Number of cyclic binary sequences of length n containing no abelian 4th powers.

2, 3, 4, 4, 4, 8, 10, 14, 12, 20, 34, 33, 52, 61, 76, 96, 126, 200, 258, 442, 568

Offset: 1

Author

Jeffrey Shallit, Jun 05 2018

Keywords

• nonn
• more

Comments

Two length-n sequences are considered to be the same in the cyclic sense if one is a cyclic shift of the other.

An abelian 4th power is a word of the form x x' x'' x''', where x', x'', x''' are all permutations of x.

Examples

			a(7) = 10, and the cyclic words are {0001001, 0001011, 0001101, 0010011, 0010101, 0010111, 0011011, 0011101, 0101011, 0110111}.