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

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =32a(5) =88a(6) =240a(7) =656a(8) =1792a(9) =4896a(10) =13376a(11) =36544a(12) =99840a(13) =272768a(14) =745216a(15) =2035968a(16) =5562368a(17) =15196672a(18) =41518080a(19) =113429504a(20) =309895168a(21) =846649344a(22) =2313089024a(23) =6319476736a(24) =17265131520a(25) =47169216512a(26) =128868696064a(27) =352075825152a(28) =961889042432