Coefficient of x^n in 1/((1+x)*(1-x)^(n-1)).

Terms

a(0) =1a(1) =-1a(2) =1a(3) =2a(4) =9a(5) =34a(6) =130a(7) =496a(8) =1897a(9) =7274a(10) =27966a(11) =107788a(12) =416394a(13) =1611908a(14) =6251596a(15) =24287212a(16) =94499689a(17) =368202778a(18) =1436458486a(19) =5610483532a(20) =21936442894a(21) =85852554748a(22) =336300861436