10626317415domain: NAppears in sequencesa(n) = 14*a(n-1) - a(n-2) + 6 for n>1, a(0)=0, a(1)=7.at n=9A001921Expansion of (1-x)^2/((1+x^2)*(1-4*x+x^2)).at n=18A099488