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A181689 Number of maximal self-avoiding walks from NW to SW corners of a 5 X n grid. 5
1, 0, 8, 0, 86, 0, 948, 0, 10444, 0, 115056, 0, 1267512, 0, 13963520, 0, 153828832, 0, 1694652176, 0, 18669100976, 0, 205667768400, 0, 2265734756752, 0, 24960420526224, 0, 274975961325264, 0, 3029267044091408, 0, 33371858326057936, 0, 367640393509287824, 0, 4050102862690348880, 0, 44617875206245953552, 0, 491531908055724064720, 0, 5414951194338345409680, 0, 59653698888134291413584, 0, 657173751585588653678864, 0, 7239741169830151881286864 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

All even terms are 0.

LINKS

Table of n, a(n) for n=1..49.

Index entries for linear recurrences with constant coefficients, signature (0,11,0,0,0,2).

FORMULA

G.f.: x*(1 - 3*x^2 - 2*x^4)/(1 - 11*x^2 - 2*x^6).

a(n) = 11*a(n-2) + 2*a(n-6) for n>6. - Wesley Ivan Hurt, Apr 10 2016

MAPLE

A181689:=proc(n) option remember:

if n mod 2 = 0 then 0 elif n=1 then 1 elif n=3 then 8 elif n=5 then 86 else 11*a(n-2)+2*a(n-6); fi; end: seq(A181689(n), n=1..50); # Wesley Ivan Hurt, Apr 10 2016

MATHEMATICA

CoefficientList[Series[(1 - 3*x^2 - 2*x^4)/(1 - 11*x^2 - 2*x^6), {x, 0, 50}], x] (* Wesley Ivan Hurt, Apr 10 2016 *)

PROG

(MAGMA) I:=[1, 0, 8, 0, 86, 0]; [n le 6 select I[n] else 11*Self(n-2)+2*Self(n-6): n in [1..50]]; // Wesley Ivan Hurt, Apr 10 2016

(PARI) x='x+O('x^99); Vec(x*(1-3*x^2-2*x^4)/(1-11*x^2-2*x^6)) \\ Altug Alkan, Apr 11 2016

CROSSREFS

Row 5 of A271592.

Cf. A000532, A003778, A006865, A014584, A014585, A181688.

Sequence in context: A186979 A067817 A079137 * A221887 A277257 A121770

Adjacent sequences:  A181686 A181687 A181688 * A181690 A181691 A181692

KEYWORD

nonn,easy,walk

AUTHOR

Sean A. Irvine, Nov 17 2010

STATUS

approved

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Last modified August 16 19:19 EDT 2018. Contains 313809 sequences. (Running on oeis4.)