Number of 2-element intersecting families (with not necessarily distinct sets) whose union is an n-element set.

A053156

Number of 2-element intersecting families (with not necessarily distinct sets) whose union is an n-element set.

Terms

    a(0) =1a(1) =3a(2) =10a(3) =33a(4) =106a(5) =333a(6) =1030a(7) =3153a(8) =9586a(9) =29013a(10) =87550a(11) =263673a(12) =793066a(13) =2383293a(14) =7158070a(15) =21490593a(16) =64504546a(17) =193579173a(18) =580868590a(19) =1742867913a(20) =5229128026a(21) =15688432653a(22) =47067395110a(23) =141206379633a(24) =423627527506

External references