a(n) = 49*n^2 - 78*n + 31.

Terms

a(0) =2a(1) =71a(2) =238a(3) =503a(4) =866a(5) =1327a(6) =1886a(7) =2543a(8) =3298a(9) =4151a(10) =5102a(11) =6151a(12) =7298a(13) =8543a(14) =9886a(15) =11327a(16) =12866a(17) =14503a(18) =16238a(19) =18071a(20) =20002a(21) =22031a(22) =24158a(23) =26383a(24) =28706a(25) =31127a(26) =33646a(27) =36263a(28) =38978a(29) =41791