a(n) = n*(29*n + 1)/2.

Terms

a(0) =0a(1) =15a(2) =59a(3) =132a(4) =234a(5) =365a(6) =525a(7) =714a(8) =932a(9) =1179a(10) =1455a(11) =1760a(12) =2094a(13) =2457a(14) =2849a(15) =3270a(16) =3720a(17) =4199a(18) =4707a(19) =5244a(20) =5810a(21) =6405a(22) =7029a(23) =7682a(24) =8364a(25) =9075a(26) =9815a(27) =10584a(28) =11382a(29) =12209