A056275 Number of primitive (aperiodic) word structures of length n using a 4-ary alphabet.

1, 1, 4, 13, 50, 181, 714, 2780, 11046, 43895, 175274, 699875, 2798250, 11188191, 44747380, 178970560, 715860650, 2863365834, 11453377194, 45813202675, 183252461532, 733008625151, 2932033104554, 11728127521060, 46912504507000, 187649998452735, 750599971438464

Offset

1,3

Comments

Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.

References

M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Links

Table of n, a(n) for n=1..27.

Formula

a(n) = Sum_{d|n} mu(d)*A007581(n/d-1).

Crossrefs

Cf. A008683, A054719.

Sequence in context: A284336 A230081 A299699 * A149455 A105968 A149456

Adjacent sequences: A056272 A056273 A056274 * A056276 A056277 A056278

Keyword

nonn

Author

Marks R. Nester

Status

approved