a(n) = 5^n*(n+1)*(4*n^2+14*n+3)/3.

Terms

a(0) =1a(1) =70a(2) =1175a(3) =13500a(4) =128125a(5) =1081250a(6) =8421875a(7) =61875000a(8) =434765625a(9) =2949218750a(10) =19443359375a(11) =125195312500a(12) =790283203125