Let T(n) = n(n+1)/2 be the n-th triangular number (A000217); a(n) = T(8T(n)).

Terms

a(0) =0a(1) =36a(2) =300a(3) =1176a(4) =3240a(5) =7260a(6) =14196a(7) =25200a(8) =41616a(9) =64980a(10) =97020a(11) =139656a(12) =195000a(13) =265356a(14) =353220a(15) =461280a(16) =592416a(17) =749700a(18) =936396a(19) =1155960a(20) =1412040a(21) =1708476a(22) =2049300a(23) =2438736a(24) =2881200a(25) =3381300a(26) =3943836a(27) =4573800a(28) =5276376a(29) =6056940