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A170877 Number of binary words of length n with properties that there is no pair of adjacent 1's and no subword of the form X^4 for any string X. 1
1, 2, 3, 5, 7, 10, 15, 22, 30, 43, 61, 88, 123, 173, 246, 348, 487, 688, 972, 1371, 1928, 2714, 3822, 5387, 7582, 10681, 15046, 21194, 29835, 42009, 59159, 83305, 117292, 165170, 232593, 327530, 461198, 649431, 914493, 1287747, 1813281, 2553346, 3595465 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
The subword 01010101 (corresponding to X = 01) for example cannot occur.
LINKS
EXAMPLE
a(3) = 5: 000, 001, 010, 100, 101.
a(4) = 7: 0001, 0010, 0100, 1000, 0101, 1010, 1001.
CROSSREFS
Sequence in context: A225490 A076972 A301756 * A003410 A362757 A018133
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(24)-a(42) from Lars Blomberg, Aug 22 2013
STATUS
approved

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Last modified May 26 04:31 EDT 2024. Contains 372807 sequences. (Running on oeis4.)