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

Terms

a(0) =0a(1) =14a(2) =57a(3) =129a(4) =230a(5) =360a(6) =519a(7) =707a(8) =924a(9) =1170a(10) =1445a(11) =1749a(12) =2082a(13) =2444a(14) =2835a(15) =3255a(16) =3704a(17) =4182a(18) =4689a(19) =5225a(20) =5790a(21) =6384a(22) =7007a(23) =7659a(24) =8340a(25) =9050a(26) =9789a(27) =10557a(28) =11354a(29) =12180