

A056521


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


4



0, 0, 0, 0, 0, 1, 1, 7, 10, 43, 65, 219, 350, 1058, 1701, 4796, 7770, 21094, 34105, 90205, 145749, 379326, 611501, 1573205, 2532530, 6465123, 10391735, 26378849, 42355950, 107089814, 171798901, 433088656, 694337225, 1746623215, 2798806984, 7029320466, 11259666950
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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

Andrew Howroyd, Table of n, a(n) for n = 1..200


FORMULA

a(n) = A056515(n)  A056514(n).
Moebius transform of A056510.  T. D. Noe, Oct 25 2006


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 A285037.
Cf. A056483, A056510, A056514, A056515.
Sequence in context: A126076 A258284 A099579 * A056510 A013398 A013493
Adjacent sequences: A056518 A056519 A056520 * A056522 A056523 A056524


KEYWORD

nonn


AUTHOR

Marks R. Nester


EXTENSIONS

Corrected by T. D. Noe, Oct 25 2006
a(17)a(30) from Andrew Howroyd, Apr 08 2017
Terms a(31) and beyond from Andrew Howroyd, Oct 01 2019


STATUS

approved



