Expansion of g.f. (1-x)/(1-12*x).

Terms

a(0) =1a(1) =11a(2) =132a(3) =1584a(4) =19008a(5) =228096a(6) =2737152a(7) =32845824a(8) =394149888a(9) =4729798656a(10) =56757583872a(11) =681091006464