login
A056338
Number of primitive (aperiodic) reversible string structures with n beads using exactly four different colors.
1
0, 0, 0, 1, 6, 37, 183, 876, 3930, 17179, 73095, 306323, 1267266, 5198374, 21182337, 85910040, 347187210, 1399447578, 5629911015, 22616239535, 90754854843, 363890053582, 1458172596903, 5840531328120, 23385650196084
OFFSET
1,5
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]
FORMULA
CROSSREFS
Column 4 of A276544.
Cf. A056320.
Sequence in context: A129552 A293800 A327611 * A056328 A156185 A057418
KEYWORD
nonn
STATUS
approved