-22369620domain: ZAppears in sequencesa(n) = -a(n-1) + 2*a(n-2), a(0)=1, a(1)=2.at n=26A084247Expansion of (1+x-4*x^2) / ((1+x)*(1-4*x^2)).at n=26A087213a(n) = (1/3)*(1 - (-2)^n + 3*(-1)^n ) = (-1)^(n+1)*A167030(n).at n=26A167193G.f.: x^2*(3+3*x+x^2) / ( (2*x+1) * (1+x) * (1+x+x^2) * (x^2-x+1) ) .at n=25A167617