Number of invertible Steinhaus matrices of order n.

Terms

a(0) =1a(1) =0a(2) =4a(3) =3a(4) =10a(5) =12a(6) =76a(7) =122a(8) =278a(9) =596a(10) =1502a(11) =3057a(12) =6758a(13) =13643a(14) =29333a(15) =59454a(16) =121967a(17) =247085a(18) =505007a(19) =1016475a(20) =2049676a(21) =4115006a(22) =8278499