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A063467
Number of idempotent reversible binary (i.e., radius one half) cellular automata of order n. Equivalently, number of loop-noded symmetric 2-colored unique 2-path graphs on n nodes. Equivalently, number of idempotent semicentral bigroupoids of order n.
1
1, 1, 1, 3, 1, 9, 1, 53, 184, 813, 1, 144802
OFFSET
1,4
COMMENTS
a(n)=1 for prime values of n as we must factor to get nontrivial examples.
REFERENCES
T. Boykett, "Combinatorial construction of one-dimensional cellular automata", Contributions to General Algebra 9, 1994.
CROSSREFS
Cf. A261864.
Sequence in context: A130599 A157674 A360752 * A223140 A021762 A019736
KEYWORD
nice,nonn,hard,more
AUTHOR
Tim Boykett (tim(AT)timesup.org), Jul 27 2001
EXTENSIONS
a(12) from Tim Boykett's 2004 article, page 244.
STATUS
approved