Expansion of g.f. (1+x-x^2)/((1-x)*(1-3*x)).

Terms

a(0) =1a(1) =5a(2) =16a(3) =49a(4) =148a(5) =445a(6) =1336a(7) =4009a(8) =12028a(9) =36085a(10) =108256a(11) =324769a(12) =974308a(13) =2922925a(14) =8768776a(15) =26306329a(16) =78918988a(17) =236756965a(18) =710270896a(19) =2130812689a(20) =6392438068a(21) =19177314205a(22) =57531942616a(23) =172595827849a(24) =517787483548