Number of strings of numbers x(i=1..n) in 0..3 with sum i*x(i)^2 equal to n*9.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =19a(5) =51a(6) =130a(7) =359a(8) =946a(9) =2333a(10) =5818a(11) =14088a(12) =33135a(13) =76611a(14) =173464a(15) =384457a(16) =837012a(17) =1790715a(18) =3766901a(19) =7802712a(20) =15923697a(21) =32039816a(22) =63611885a(23) =124689752a(24) =241431996a(25) =462031599a(26) =874300348a(27) =1636607223a(28) =3031814449a(29) =5560277156