a(n) = a(n-1) + 3*a(n-2) -2*a(n-3) - 2*a(n-4), where a(0) = -1, a(1) = 0, a(2) = 1, a(3) = 1.

Terms

a(0) =-1a(1) =0a(2) =1a(3) =1a(4) =6a(5) =7a(6) =21a(7) =28a(8) =65a(9) =93a(10) =190a(11) =283a(12) =537a(13) =820a(14) =1485a(15) =2305a(16) =4046a(17) =6351a(18) =10909a(19) =17260a(20) =29193a(21) =46453a(22) =77694a(23) =124147a(24) =205937a(25) =330084a(26) =544213a(27) =874297a(28) =1434894a(29) =2309191