OFFSET
0,2
COMMENTS
A131244 is a companion sequence.
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,3,-1,-1)
FORMULA
G.f. -(1+x)*(x^2-x-1)/ ( 1-x-3*x^2+x^3+x^4 ). - R. J. Mathar, Jan 29 2011
a(0)=1, a(1)=3, a(2)=6, a(3)=13, a(n)=a(n-1)+3*a(n-2)-a(n-3)-a(n-4). - Harvey P. Dale, Sep 07 2013
EXAMPLE
a(3) = 13 = sum of row 3 terms of triangle A131245: (5 + 5 + 2 + 1)
MAPLE
MATHEMATICA
CoefficientList[Series[-(1+x)(x^2-x-1)/(1-x-3x^2+x^3+x^4), {x, 0, 30}], x] (* or *) LinearRecurrence[{1, 3, -1, -1}, {1, 3, 6, 13}, 30] (* Harvey P. Dale, Sep 07 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Gary W. Adamson, Jun 22 2007
STATUS
approved