Number of homeomorphically irreducible general graphs on 4 labeled nodes and with n edges.

Terms

a(0) =1a(1) =6a(2) =19a(3) =68a(4) =242a(5) =704a(6) =1981a(7) =5140a(8) =12364a(9) =27614a(10) =57598a(11) =113108a(12) =210812a(13) =375606a(14) =643646a(15) =1066196a(16) =1714445a(17) =2685464a(18) =4109493a(19) =6158768a(20) =9058119a(21) =13097592a(22) =18647371a(23) =26175300a(24) =36267330a(25) =49651242a(26) =67224024a(27) =90083308a(28) =119563302