a(n) = 5*n^2 + 1.

Terms

a(0) =1a(1) =6a(2) =21a(3) =46a(4) =81a(5) =126a(6) =181a(7) =246a(8) =321a(9) =406a(10) =501a(11) =606a(12) =721a(13) =846a(14) =981a(15) =1126a(16) =1281a(17) =1446a(18) =1621a(19) =1806a(20) =2001a(21) =2206a(22) =2421a(23) =2646a(24) =2881a(25) =3126a(26) =3381a(27) =3646a(28) =3921a(29) =4206