a(n) = C(2,n) DELTA C(0,n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =1a(6) =11a(7) =17a(8) =7a(9) =1a(10) =41a(11) =72a(12) =40a(13) =10a(14) =1a(15) =153a(16) =301a(17) =208a(18) =72a(19) =13a(20) =1a(21) =571a(22) =1244a(23) =1021a(24) =446a(25) =113a(26) =16a(27) =1a(28) =2131a(29) =5093