a(n) = (2*n-1)*(13*n^2-13*n+6)/6.

Terms

a(0) =1a(1) =16a(2) =70a(3) =189a(4) =399a(5) =726a(6) =1196a(7) =1835a(8) =2669a(9) =3724a(10) =5026a(11) =6601a(12) =8475a(13) =10674a(14) =13224a(15) =16151a(16) =19481a(17) =23240a(18) =27454a(19) =32149a(20) =37351a(21) =43086a(22) =49380a(23) =56259a(24) =63749a(25) =71876a(26) =80666a(27) =90145a(28) =100339a(29) =111274