Number of connected graphs with n edges.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =5a(5) =12a(6) =30a(7) =79a(8) =227a(9) =710a(10) =2322a(11) =8071a(12) =29503a(13) =112822a(14) =450141a(15) =1867871a(16) =8037472a(17) =35787667a(18) =164551477a(19) =779945969a(20) =3804967442a(21) =19079312775a(22) =98211456209a(23) =518397621443