Squares mod 42.

Terms

a(0) =0a(1) =1a(2) =4a(3) =7a(4) =9a(5) =15a(6) =16a(7) =18a(8) =21a(9) =22a(10) =25a(11) =28a(12) =30a(13) =36a(14) =37a(15) =39