a(n+1) = a(n-3) + a(n-2) - a(n-1) + a(n) starting with 1, 2, 3, 4.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =4a(5) =5a(6) =8a(7) =11a(8) =12a(9) =14a(10) =21a(11) =30a(12) =35a(13) =40a(14) =56a(15) =81a(16) =100a(17) =115a(18) =152a(19) =218a(20) =281a(21) =330a(22) =419a(23) =588a(24) =780a(25) =941a(26) =1168a(27) =1595a(28) =2148a(29) =2662