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A124721 Number of ternary Lyndon words with exactly three 1's. 5
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; text; internal format)
OFFSET

4,1

LINKS

Table of n, a(n) for n=4..31.

Index entries for linear recurrences with constant coefficients, signature (6,-12,10,-12,24,-16).

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

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

CROSSREFS

Cf. A051168, A027376, A124720, A124722, A124723.

Sequence in context: A097040 A302237 A224289 * A279735 A103453 A024023

Adjacent sequences:  A124718 A124719 A124720 * A124722 A124723 A124724

KEYWORD

nonn,easy

AUTHOR

Mike Zabrocki, Nov 05 2006

STATUS

approved

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Last modified September 23 11:51 EDT 2021. Contains 347612 sequences. (Running on oeis4.)