

A216215


Number of (weakly) superprimitive binary sequences of length n.


2



1, 2, 2, 6, 12, 28, 54, 118, 230, 490, 968, 1980, 3978, 8066, 16100, 32494, 64994, 130468, 261000, 523092, 1046292, 2094812, 4189704, 8383732, 16768206, 33545152, 67090578, 134199252, 268399910, 536834026, 1073671504, 2147411556, 4294826718, 8589792856, 17179592372, 34359455674
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OFFSET

0,2


COMMENTS

A string x of length n is (strongly) quasiperiodic if there exists a string w of length < n such that x can be exactly covered by (possibly overlapping) occurrences of w in x. For example, 01001010 can be covered by 3 occurrences of 010. A string is (weakly) superprimitive if it is not strongly quasiperiodic.


LINKS



EXAMPLE

a(4) = 12 because the 6 strings
0001,
0010,
0011,
0100,
0110,
0111
and their complements are the only weakly superprimitive strings of length 4.


PROG

(C) See Links section.


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



