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

Author

Marks R. Nester

Keywords

• nonn

Examples

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

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

Crossrefs

Column 3 of A285012.

Cf. A000392, A056503, A056504, A056519.

Formula

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

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

Extensions

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

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