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A056510
Number of periodic palindromic structures of length n using exactly four different symbols.
3
0, 0, 0, 0, 0, 1, 1, 7, 10, 43, 65, 220, 350, 1059, 1701, 4803, 7770, 21105, 34105, 90248, 145750, 379391, 611501, 1573432, 2532530, 6465473, 10391745, 26379908, 42355950, 107091559, 171798901, 433093459, 694337290, 1746630985, 2798806985, 7029341790, 11259666950
OFFSET
1,8
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
FORMULA
a(n) = A056505(n) - A056504(n).
Inverse Moebius transform of A056521. - 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 4 of A285012.
Sequence in context: A258284 A099579 A056521 * A013398 A013493 A166661
KEYWORD
nonn
EXTENSIONS
Corrected by T. D. Noe, Oct 25 2006
a(17)-a(30) from Andrew Howroyd, Apr 07 2017
Terms a(31) and beyond from Andrew Howroyd, Oct 01 2019
STATUS
approved