a(n) is the smallest square s > 0 such that s*(2n+1) is a triangular number.

Terms

a(0) =1a(1) =1a(2) =9a(3) =4a(4) =4a(5) =441a(6) =25a(7) =1a(8) =9a(9) =9a(10) =1a(11) =3218436a(12) =49a(13) =1089a(14) =1656369a(15) =16a(16) =16a(17) =225a(18) =46225a(19) =9a(20) =81a(21) =314721a(22) =1a(23) =12217323024a(24) =25a(25) =25a(27) =1a(28) =2304a(29) =199572129a(30) =121