A215072 Number of squarefree words of length n in a 6-ary alphabet, with new values 0..5 introduced in increasing order.

1, 1, 2, 4, 12, 40, 153, 638, 2825, 12938, 60458, 285664, 1358283, 6480694, 30979999, 148249768, 709832688, 3399805736, 16286469156, 78026226228, 373832145200, 1791120945112

Offset

1,3

Comments

Column 5 of A215075.

Links

Table of n, a(n) for n=1..22.

Example

Some solutions for n=9
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1
..2....2....2....2....2....2....2....2....2....2....0....2....0....2....2....2
..3....1....0....3....0....3....3....0....3....0....2....0....2....3....0....3
..4....3....3....0....3....4....2....3....1....3....1....3....1....4....3....4
..3....2....0....2....2....5....0....0....2....0....3....4....2....2....4....2
..5....4....2....4....3....3....2....4....4....2....0....3....0....3....1....0
..0....3....4....3....4....4....1....3....5....4....1....2....1....0....0....2
..3....4....2....5....3....1....4....5....4....0....3....0....0....2....2....3

Crossrefs

Cf. A215075.

Sequence in context: A119430 A074034 A268952 * A326513 A268953 A268954

Adjacent sequences: A215069 A215070 A215071 * A215073 A215074 A215075

Keyword

nonn

Author

R. H. Hardin, Aug 02 2012

Status

approved