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

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =26a(6) =61a(7) =147a(8) =339a(9) =771a(10) =1721a(11) =3770a(12) =8123a(13) =17233a(14) =36041a(15) =74322a(16) =151368a(17) =304614a(18) =606305a(19) =1194266a(20) =2329462a(21) =4501905a(22) =8624652a(23) =16386814a(24) =30891283a(25) =57801169a(26) =107387377a(27) =198165046a(28) =363321016a(29) =662012254