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A351364
Number of necklaces with n black and n white beads that avoid the pattern BBBB.
1
1, 2, 4, 9, 21, 59, 162, 483, 1453, 4492, 14048, 44616, 142936, 462380, 1506534, 4941955, 16303783, 54066560, 180111432, 602481589, 2022797529, 6814336663, 23026359634, 78027238290, 265085903996, 902733374480, 3080967048004, 10536594982790, 36102498293396, 123920278459564
OFFSET
1,2
LINKS
Marko R. Riedel et al., Necklaces made of black and white beads, Math StackExchange, Feb 2022.
FORMULA
a(n) = A003239(n) - A351363(n).
CROSSREFS
KEYWORD
nonn
AUTHOR
Marko Riedel, Feb 08 2022
STATUS
approved