Number of strings of numbers x(i=1..n) in 0..4 with sum i*x(i) equal to n*4.

Terms

a(0) =1a(1) =3a(2) =9a(3) =28a(4) =78a(5) =207a(6) =504a(7) =1169a(8) =2574a(9) =5439a(10) =11071a(11) =21841a(12) =41846a(13) =78193a(14) =142787a(15) =255441a(16) =448444a(17) =773966a(18) =1314861a(19) =2201731a(20) =3637642a(21) =5935817a(22) =9574284a(23) =15277075a(24) =24130784a(25) =37755124a(26) =58545388a(27) =90021407a(28) =137320211a(29) =207895383