Number of strings of numbers x(i=1..n) in 0..3 with sum i*x(i) equal to n*3.

Terms

a(0) =1a(1) =2a(2) =6a(3) =14a(4) =34a(5) =74a(6) =154a(7) =304a(8) =580a(9) =1066a(10) =1901a(11) =3304a(12) =5610a(13) =9332a(14) =15241a(15) =24476a(16) =38721a(17) =60418a(18) =93088a(19) =141765a(20) =213590a(21) =318608a(22) =470873a(23) =689907a(24) =1002660a(25) =1446141a(26) =2070897a(27) =2945590a(28) =4163079a(29) =5848345