A056518 - OEIS

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A056518

Number of primitive (period n) periodic palindromic structures using exactly two different symbols.

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 A347734 A267459

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