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A128016
Expansion of (1+x+x^2+x^3)/(1-x^2+x^4).
1
1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1
OFFSET
0,3
COMMENTS
Periodic{1,1,2,2,1,1,-1,-1,-2,-2,-1,-1}.
FORMULA
G.f.: (1-x^4)/(1-x-x^2+x^3+x^4-x^5); a(n)=cos(5*pi*n/6)/2+(1-sqrt(3)/2)sin(5*pi*n/6)+cos(pi*n/6)/2+(1+sqrt(3)/2)sin(pi*n/6);
MATHEMATICA
CoefficientList[Series[(1+x+x^2+x^3)/(1-x^2+x^4), {x, 0, 100}], x] (* or *) LinearRecurrence[{0, 1, 0, -1}, {1, 1, 2, 2}, 100] (* Harvey P. Dale, Aug 02 2015 *)
CROSSREFS
Cf. A128017.
Sequence in context: A138385 A030614 A328615 * A128017 A096285 A328483
KEYWORD
easy,sign
AUTHOR
Paul Barry, Feb 11 2007
STATUS
approved