a(n) = binomial(4*n,4).

Terms

a(0) =1a(1) =70a(2) =495a(3) =1820a(4) =4845a(5) =10626a(6) =20475a(7) =35960a(8) =58905a(9) =91390a(10) =135751a(11) =194580a(12) =270725a(13) =367290a(14) =487635a(15) =635376a(16) =814385a(17) =1028790a(18) =1282975a(19) =1581580a(20) =1929501a(21) =2331890a(22) =2794155a(23) =3321960a(24) =3921225a(25) =4598126a(26) =5359095a(27) =6210820a(28) =7160245a(29) =8214570