a(n) = 42*n^2 - 1.

Terms

a(0) =41a(1) =167a(2) =377a(3) =671a(4) =1049a(5) =1511a(6) =2057a(7) =2687a(8) =3401a(9) =4199a(10) =5081a(11) =6047a(12) =7097a(13) =8231a(14) =9449a(15) =10751a(16) =12137a(17) =13607a(18) =15161a(19) =16799a(20) =18521a(21) =20327a(22) =22217a(23) =24191a(24) =26249a(25) =28391a(26) =30617a(27) =32927a(28) =35321a(29) =37799