Number of n X n circulant invertible (0,1) matrices over the reals.

Terms

a(0) =1a(1) =2a(2) =6a(3) =8a(4) =30a(5) =36a(6) =126a(7) =160a(8) =450a(9) =740a(10) =2046a(11) =2592a(12) =8190a(13) =12824a(14) =30030a(15) =48640a(16) =131070a(17) =194508a(18) =524286a(19) =812840a(20) =1987818a(21) =3486824a(22) =8388606a(23) =12400368a(24) =33348150a(25) =56700072a(26) =128800098a(27) =219681672a(28) =536870910a(29) =861181320