Reduced interval graphs with n nodes.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =7a(7) =31a(8) =168a(9) =1025a(10) =7013a(11) =52495a(12) =425213a(13) =3696032a(14) =34291937a(15) =338161526a(16) =3532185118a(17) =38963334652a(18) =452704892533