a(n) = F(n)*F(n-1) if n odd otherwise F(n)*F(n-1)-1, where F = Fibonacci numbers A000045.

Terms

a(0) =0a(1) =0a(2) =2a(3) =5a(4) =15a(5) =39a(6) =104a(7) =272a(8) =714a(9) =1869a(10) =4895a(11) =12815a(12) =33552a(13) =87840a(14) =229970a(15) =602069a(16) =1576239a(17) =4126647a(18) =10803704a(19) =28284464a(20) =74049690a(21) =193864605a(22) =507544127a(23) =1328767775a(24) =3478759200a(25) =9107509824a(26) =23843770274a(27) =62423800997a(28) =163427632719a(29) =427859097159