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A056509 Number of periodic palindromic structures of length n using exactly three different symbols. 4
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 17 06:06 EST 2019. Contains 329217 sequences. (Running on oeis4.)