Dying rabbits: a(n) = a(n-1) + a(n-2) - a(n-4).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =3a(5) =4a(6) =6a(7) =8a(8) =11a(9) =15a(10) =20a(11) =27a(12) =36a(13) =48a(14) =64a(15) =85a(16) =113a(17) =150a(18) =199a(19) =264a(20) =350a(21) =464a(22) =615a(23) =815a(24) =1080a(25) =1431a(26) =1896a(27) =2512a(28) =3328a(29) =4409