OFFSET
0,3
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
Andrew Howroyd, Table of n, a(n) for n = 0..200
FORMULA
a(n) = Sum_{k=1..4} A285012(n, k) for n > 0. - Andrew Howroyd, Oct 01 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected by T. D. Noe, Oct 25 2006
a(0)=1 prepended and terms a(17) and beyond from Andrew Howroyd, Oct 01 2019
STATUS
approved