a(n) = 4*(n+1)^2*(3*n+1)^2*(12*n^2+20*n+5).

Terms

a(0) =20a(1) =9472a(2) =164052a(3) =1107200a(4) =4681300a(5) =14929920a(6) =39411092a(7) =90821632a(8) =188932500a(9) =362835200a(10) =653499220a(11) =1116640512a(12) =1825901012a(13) =2876339200a(14) =4388231700a(15) =6511185920a(16) =9428563732a(17) =13362216192a(18) =18577529300a(19) =25388780800a(20) =34164808020