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A124722
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Number of ternary Lyndon words with exactly four 1's.
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5
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2, 9, 40, 137, 448, 1336, 3840, 10540, 28160, 73168, 186368, 465808, 1146880, 2785024, 6684672, 15875520, 37355520, 87161600, 201850880, 464254208, 1061158912, 2411718656, 5452595200, 12268325888, 27481079808, 61303918592
(list; graph; refs; listen; history; internal format)
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OFFSET
| 5,1
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FORMULA
| G.f.: x^5*(2-3*x)*(1-x)^2/(1 - 2*x^2)^2/(1 - 2*x)^4 = (1/(1-2*x)^4-1/(1-2*x^2)^2)/4
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EXAMPLE
| a(6) = 9 because 111122, 111212, 111123, 111213, 112113, 111132, 111312, 111133, 111313 are all ternary Lyndon words with four 1's
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CROSSREFS
| Cf. A051168, A027376, A124720, A124721, A124723.
Sequence in context: A020002 A120700 A075873 * A019066 A097070 A164033
Adjacent sequences: A124719 A124720 A124721 * A124723 A124724 A124725
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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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