A215396 Number of length-n 0..3 arrays connected end-around, with no sequence of L<n elements immediately followed by itself (periodic "squarefree"), and new values introduced in order 0..3.

1, 1, 1, 3, 5, 17, 35, 102, 240, 665, 1661, 4501, 11466, 30366, 78990, 208272, 543065, 1427121, 3733443, 9798235, 25661293, 67307229, 176371866, 462472478

Offset

1,4

Comments

Column 3 of A215401.

Links

Table of n, a(n) for n=1..24.

Example

Some solutions for n=6:
..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....0....2....2....2....2....0....2....2....0....2....0....2
..3....3....1....3....2....0....0....1....1....2....0....0....2....3....2....0
..2....0....0....1....1....1....2....3....0....0....2....3....3....1....1....3
..1....2....2....3....3....3....3....2....3....3....1....1....2....2....2....2

Crossrefs

Sequence in context: A148508 A148509 A148510 * A130844 A148511 A148512

Adjacent sequences: A215393 A215394 A215395 * A215397 A215398 A215399

Keyword

nonn

Author

R. H. Hardin, Aug 09 2012

Status

approved