a(n) is the minimal number of legal positions in Go played on connected graphs with n nodes.

Terms

a(0) =1a(1) =5a(2) =15a(3) =41a(4) =107a(5) =273a(6) =707a(7) =1817a(8) =4617a(9) =11867a(10) =30425a(11) =76857a(12) =197603a(13) =505871a(14) =1275465a(15) =3276563a(16) =8406527a(17) =21165273a(18) =54338627a(19) =139513379a(20) =351447657a(21) =901789811a(22) =2304725075a(23) =5840498937a(24) =14978318243a(25) =38107010435a(26) =97141424265a(27) =248995117523a(28) =630641012147