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!)
A226493 Closed walks of length n in K_4 graph. 2
0, 12, 24, 84, 240, 732, 2184, 6564, 19680, 59052, 177144, 531444, 1594320, 4782972, 14348904, 43046724, 129140160, 387420492, 1162261464, 3486784404, 10460353200, 31381059612, 94143178824, 282429536484, 847288609440, 2541865828332, 7625597484984, 22876792454964 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Essentially the same as A218034.

REFERENCES

Mike Krebs and Tony Shaheen, Expander Families and Cayley Graphs, Oxford University Press, Inc. 2011

LINKS

Table of n, a(n) for n=1..28.

K. Böhmová, C. Dalfó, C. Huemer, On cyclic Kautz digraphs, Preprint 2016.

Cristina Dalfó, From subKautz digraphs to cyclic Kautz digraphs, arXiv:1709.01882 [math.CO], 2017.

C. Dalfó, The spectra of subKautz and cyclic Kautz digraphs, Linear Algebra and its Applications, 531 (2017), p. 210-219.

Index entries for linear recurrences with constant coefficients, signature (2,3).

FORMULA

a(n) = 3*(-1)^n + 3^n = 12*A015518(n-1).

G.f.: 12*x^2 / ( (1+x)*(1-3*x) ). - R. J. Mathar, Jun 29 2013

MATHEMATICA

Table[3 (-1)^k + 3^k, {k, 30}]

PROG

(PARI) a(n) = { 3*(-1)^n + 3^n } \\ Andrew Howroyd, Sep 11 2019

CROSSREFS

Column k=4 of A106512.

Cf. A218034.

Sequence in context: A120360 A120356 A109745 * A051385 A290304 A289335

Adjacent sequences:  A226490 A226491 A226492 * A226494 A226495 A226496

KEYWORD

nonn,easy

AUTHOR

Gustavo Gordillo, Jun 09 2013

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 February 16 16:00 EST 2020. Contains 331961 sequences. (Running on oeis4.)