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A212586 Nonnegative walks of length n on the x-axis starting at the origin using steps {1,0,-1} and visiting no point more than twice. 5
1, 2, 6, 13, 29, 60, 128, 269, 569, 1198, 2526, 5321, 11213, 23624, 49776, 104873, 220961, 465546, 980870, 2066613, 4354189, 9173924, 19328720, 40724053, 85802297, 180778518, 380885758, 802495569, 1690793437, 3562365392, 7505616544, 15813728657, 33318250753 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Note: a 0 step counts as a visit and a step but does not contribute to the length of the walk.

LINKS

Table of n, a(n) for n=0..32.

FORMULA

G.f.: (1+x^2+x^3-x^5)/(1-2*x-x^2+2*x^3-x^4+x^6).

MATHEMATICA

CoefficientList[Series[ (1+x^2+x^3-x^5)/(1-2*x-x^2+2*x^3-x^4+x^6) , {x, 0, 45}], x]

CROSSREFS

Cf. A212584, A212585, A212587, A164392, A212589.

Sequence in context: A289887 A055243 A173009 * A276411 A180965 A075632

Adjacent sequences:  A212583 A212584 A212585 * A212587 A212588 A212589

KEYWORD

nonn,easy,walk

AUTHOR

David Scambler, May 22 2012

STATUS

approved

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Last modified September 20 08:08 EDT 2019. Contains 327214 sequences. (Running on oeis4.)