Expansion of g.f.: (1+x+x^2)/(1-5*x-5*x^2).

Terms

a(0) =1a(1) =6a(2) =36a(3) =210a(4) =1230a(5) =7200a(6) =42150a(7) =246750a(8) =1444500a(9) =8456250a(10) =49503750a(11) =289800000a(12) =1696518750a(13) =9931593750a(14) =58140562500a(15) =340360781250