A056521 - OEIS

A056521

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

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: A341736 A258284 A099579 * A056510 A013398 A013493

Adjacent sequences: A056518 A056519 A056520 * A056522 A056523 A056524