288959domain: NAppears in sequencesExpansion of (1-x)/(1-x+2*x^2-x^3).at n=45A078019a(n) = 3*a(n-1) - 2*a(n-2) - a(n-3), with a(0)=1, a(1)=3 and a(2)=7.at n=21A368205