login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A124722 Number of ternary Lyndon words with exactly four 1's. 5
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; text; internal format)
OFFSET

5,1

LINKS

Table of n, a(n) for n=5..30.

Index entries for linear recurrences with constant coefficients, signature (8,-20,0,76,-96,-32,128,-64).

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

EXAMPLE

a(6) = 9 because 111122, 111212, 111123, 111213, 112113, 111132, 111312, 111133, 111313 are all ternary Lyndon words with four 1's

MATHEMATICA

LinearRecurrence[{8, -20, 0, 76, -96, -32, 128, -64}, {2, 9, 40, 137, 448, 1336, 3840, 10540}, 40] (* Harvey P. Dale, Nov 04 2020 *)

CROSSREFS

Cf. A051168, A027376, A124720, A124721, A124723.

Sequence in context: A346687 A120700 A075873 * A317129 A220309 A019066

Adjacent sequences:  A124719 A124720 A124721 * A124723 A124724 A124725

KEYWORD

nonn,easy

AUTHOR

Mike Zabrocki, Nov 05 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 19 15:05 EDT 2021. Contains 348091 sequences. (Running on oeis4.)