OFFSET
0,3
COMMENTS
Paths are not required to be self-avoiding. - Andrew Howroyd, Nov 05 2019
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (18,-44,-168).
FORMULA
G.f.: (2*x^2)/((1 + 2*x)*(1 - 6*x)*(1 - 14*x)).
a(0)=0, a(1)=0, a(2)=2, a(n)=18*a(n-1)-44*a(n-2)-168*a(n-3). - Harvey P. Dale, Mar 09 2013
MATHEMATICA
CoefficientList[Series[(2x^2)/((1+2x)(1-6x)(1-14x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{18, -44, -168}, {0, 0, 2}, 30] (* Harvey P. Dale, Mar 09 2013 *)
PROG
(PARI) concat([0, 0], Vec(2/((1 + 2*x)*(1 - 6*x)*(1 - 14*x)) + O(x^20))) \\ Andrew Howroyd, Nov 05 2019
CROSSREFS
KEYWORD
nonn,walk
AUTHOR
EXTENSIONS
More terms from Harvey P. Dale, Mar 09 2013
STATUS
approved