Expansion of g.f.: (1+x)/(1-11*x).

Terms

a(0) =1a(1) =12a(2) =132a(3) =1452a(4) =15972a(5) =175692a(6) =1932612a(7) =21258732a(8) =233846052a(9) =2572306572a(10) =28295372292a(11) =311249095212