a(n) = 2*n*Fibonacci(n-2) + (-1)^n + 1.

Terms

a(0) =2a(1) =6a(2) =10a(3) =20a(4) =38a(5) =70a(6) =130a(7) =234a(8) =422a(9) =748a(10) =1322a(11) =2314a(12) =4034a(13) =6990a(14) =12066a(15) =20740a(16) =35534a(17) =60686a(18) =103362a(19) =175602a(20) =297662a(21) =503516a(22) =850130a(23) =1432850a(24) =2411138a(25) =4051350a(26) =6798010a(27) =11392244a(28) =19068662a(29) =31882198