a(n) = n*(n+1)*(n+2)*(n+3)*(2*n+1)/12.

Terms

a(0) =0a(1) =6a(2) =50a(3) =210a(4) =630a(5) =1540a(6) =3276a(7) =6300a(8) =11220a(9) =18810a(10) =30030a(11) =46046a(12) =68250a(13) =98280a(14) =138040a(15) =189720a(16) =255816a(17) =339150a(18) =442890a(19) =570570a(20) =726110a(21) =913836a(22) =1138500a(23) =1405300a(24) =1719900a(25) =2088450a(26) =2517606a(27) =3014550a(28) =3587010a(29) =4243280