A056509 Number of periodic palindromic structures of length n using exactly three different symbols.

0, 0, 0, 1, 1, 5, 6, 19, 25, 64, 90, 208, 301, 656, 966, 2035, 3025, 6250, 9330, 19035, 28501, 57740, 86526, 174436, 261625, 525994, 788970, 1583119, 2375101, 4760516, 7141686, 14303011, 21457825, 42954850, 64439010, 128953341, 193448101, 387046700, 580606446, 1161504423

Offset

1,6

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

Andrew Howroyd, Table of n, a(n) for n = 1..200

Formula

a(n) = A056504(n) - A056503(n).

Inverse Moebius transform of A056519. - Andrew Howroyd, Oct 01 2019

Example

For example, aaabbb is not a (finite) palindrome but it is a periodic palindrome. Permuting the symbols will not change the structure.

Crossrefs

Column 3 of A285012.

Cf. A000392, A056503, A056504, A056519.

Sequence in context: A031448 A290254 A163772 * A129722 A133608 A317444

Adjacent sequences: A056506 A056507 A056508 * A056510 A056511 A056512

Keyword

nonn

Author

Marks R. Nester

Extensions

a(17)-a(35) from Andrew Howroyd, Apr 07 2017

Terms a(36) and beyond from Andrew Howroyd, Oct 01 2019

Status

approved