

A323446


Number of binary strings w of length n that cannot be written in the form xyz, with x,z both nonempty and xz a square.


0



2, 2, 4, 6, 8, 12, 16, 26, 36, 70, 104, 220, 372, 758, 1408, 2874, 5472, 11056, 21696, 43546, 86060, 172514, 343068, 686888, 1369484, 2740080, 5471464, 10945900, 21872228, 43749868, 87460604, 174645564, 348957458
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OFFSET

1,1


COMMENTS

A square is a nonempty block of the form XX.


LINKS

Table of n, a(n) for n=1..33.


EXAMPLE

For n = 6 the 12 solutions are {000001, 000011, 000111, 001011, 001111, 011111} and their complements.


CROSSREFS

Sequence in context: A080054 A108494 A078578 * A018129 A091915 A123862
Adjacent sequences: A323443 A323444 A323445 * A323447 A323448 A323449


KEYWORD

nonn,more


AUTHOR

Jeffrey Shallit, Jan 15 2019


EXTENSIONS

a(21)a(33) from Lars Blomberg, Jan 26 2019


STATUS

approved



