Number of distinct n X 2 toroidal binary arrays.

Terms

a(0) =3a(1) =7a(2) =14a(3) =40a(4) =108a(5) =362a(6) =1182a(7) =4150a(8) =14602a(9) =52588a(10) =190746a(11) =699600a(12) =2581428a(13) =9588742a(14) =35792568a(15) =134223910a(16) =505294128a(17) =1908896442a(18) =7233642930a(19) =27487869472a(20) =104715443852a(21) =399822696082