A056337 Number of primitive (aperiodic) reversible string structures with n beads using exactly three different colors.

0, 0, 1, 4, 15, 49, 160, 498, 1544, 4715, 14356, 43420, 131145, 394990, 1188564, 3572400, 10732065, 32224216, 96733636, 290317660, 871200664, 2614083394, 7843255300, 23531731530, 70599259170, 211805771345

Offset

1,4

Comments

A string and its reverse are considered to be equivalent. Permuting the colors will not change the 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..26.

Formula

A056332(n)-A056331(n).

Crossrefs

Column 3 of A276544.

Cf. A056319.

Sequence in context: A320460 A178704 A099167 * A053406 A225265 A143215

Adjacent sequences: A056334 A056335 A056336 * A056338 A056339 A056340

Keyword

nonn

Author

Marks R. Nester

Status

approved