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A056518 Number of primitive (period n) periodic palindromic structures using exactly two different symbols. 1
0, 1, 1, 2, 3, 4, 7, 10, 14, 21, 31, 42, 63, 91, 123, 184, 255, 371, 511, 750, 1015, 1519, 2047, 3030, 4092, 6111, 8176, 12222, 16383, 24486, 32767, 49024, 65503, 98175, 131061, 196308, 262143, 392959, 524223, 785910, 1048575, 1572256, 2097151, 3144702, 4194162 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

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

Table of n, a(n) for n=1..45.

FORMULA

A056513(n)-A000007(n-1).

CROSSREFS

Column 2 of A285037.

Cf. A056481.

Sequence in context: A035565 A240489 A056513 * A160644 A267459 A145467

Adjacent sequences:  A056515 A056516 A056517 * A056519 A056520 A056521

KEYWORD

nonn

AUTHOR

Marks R. Nester

EXTENSIONS

a(17)-a(45) from Andrew Howroyd, Apr 08 2017

STATUS

approved

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Last modified July 23 22:38 EDT 2019. Contains 325278 sequences. (Running on oeis4.)