a(n) = a(n-1) + a(n-2) + a(n-3), with a(0) = 3, a(1) = 2, a(2) = 5.

Terms

a(0) =3a(1) =2a(2) =5a(3) =10a(4) =17a(5) =32a(6) =59a(7) =108a(8) =199a(9) =366a(10) =673a(11) =1238a(12) =2277a(13) =4188a(14) =7703a(15) =14168a(16) =26059a(17) =47930a(18) =88157a(19) =162146a(20) =298233a(21) =548536a(22) =1008915a(23) =1855684a(24) =3413135a(25) =6277734a(26) =11546553a(27) =21237422a(28) =39061709a(29) =71845684