Number of nonsquare simple imperfect squared rectangles of order n up to symmetry.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =1a(9) =0a(10) =0a(11) =9a(12) =33a(13) =104a(14) =280a(15) =948a(16) =3014a(17) =9494a(18) =30302a(19) =98897a(20) =323372a(21) =1080168a(22) =3666666a(23) =12604812a(24) =43734613a(25) =153788715