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A007727
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Number of 2n-bead black-white strings with n black beads and fundamental period 2n.
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6
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1, 2, 4, 18, 64, 250, 900, 3430, 12800, 48600, 184500, 705430, 2703168, 10400598, 40113164, 155117250, 601067520, 2333606218, 9075085776, 35345263798, 137846344000, 538257870990, 2104098258284, 8233430727598, 32247600966144
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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LINKS
| Y. Puri and T. Ward, Arithmetic and growth of periodic orbits, J. Integer Seqs., Vol. 4 (2001), #01.2.1.
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FORMULA
| Sum mu(n/d).C(2d, d); d|n.
a(0)=1, a(n) = n * A060165(n) = 2n * A022553(n). - Ralf Stephan (ralf(AT)ark.in-berlin.de), Sep 01 2003
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CROSSREFS
| Equals 2 * A045630(n), n>0.
Sequence in context: A083694 A179040 A009679 * A052689 A139104 A014448
Adjacent sequences: A007724 A007725 A007726 * A007728 A007729 A007730
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KEYWORD
| nonn
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AUTHOR
| Doug Bowman, bowman(AT)math.uiuc.edu.
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