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A124721
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Number of ternary Lyndon words with exactly three 1's.
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5
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2, 8, 26, 80, 224, 596, 1536, 3840, 9384, 22528, 53248, 124240, 286720, 655360, 1485472, 3342336, 7471104, 16602432, 36700160, 80740352, 176859776, 385875968, 838860800, 1817531648, 3925868544, 8455716864, 18164132352, 38923141120
(list; graph; refs; listen; history; internal format)
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OFFSET
| 4,1
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FORMULA
| G.f.: 2*x^4*(x - 1)^2/(1-2*x^3)/(1-2*x)^3 = (x^3/(1-2*x)^3-x^3/(1-2*x^3))/3
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EXAMPLE
| a(5) = 8 because 11122, 11212, 11123, 11132, 11213, 11312, 11133, 11313 are all ternary Lyndon words of length 5 with three 1's
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CROSSREFS
| Cf. A051168, A027376, A124720, A124722, A124723.
Sequence in context: A136594 A167826 A097040 * A024023 A103453 A126966
Adjacent sequences: A124718 A124719 A124720 * A124722 A124723 A124724
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KEYWORD
| nonn
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AUTHOR
| Mike Zabrocki (zabrocki(AT)mathstat.yorku.ca), Nov 05 2006
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