a(n) = n*(15*n - 1)/2.

Terms

a(0) =0a(1) =7a(2) =29a(3) =66a(4) =118a(5) =185a(6) =267a(7) =364a(8) =476a(9) =603a(10) =745a(11) =902a(12) =1074a(13) =1261a(14) =1463a(15) =1680a(16) =1912a(17) =2159a(18) =2421a(19) =2698a(20) =2990a(21) =3297a(22) =3619a(23) =3956a(24) =4308a(25) =4675a(26) =5057a(27) =5454a(28) =5866a(29) =6293