k-1 for integers k>=4 such that 2^k == 4 (mod k*(k-1)*(k-2)*(k-3)/24).

Terms

a(0) =3a(1) =5a(2) =37a(3) =44101a(4) =157081a(5) =2031121a(6) =7282801a(7) =8122501a(8) =18671941a(9) =78550201a(10) =208168381a(11) =770810041a(12) =2658625201a(13) =2710529641a(14) =5241663001a(15) =14643783001a(16) =18719308441a(17) =56181482281a(18) =73303609681a(19) =74623302001a(20) =110102454001a(21) =140659081201