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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
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]
FORMULA
A056513(n)-A000007(n-1).
CROSSREFS
Column 2 of A285037.
Cf. A056481.
Sequence in context: A035565 A240489 A056513 * A160644 A389823 A347734
KEYWORD
nonn
EXTENSIONS
a(17)-a(45) from Andrew Howroyd, Apr 08 2017
STATUS
approved