Number of unlabeled 2,3 cacti (triangular cacti with bridges).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =16a(6) =41a(7) =106a(8) =304a(9) =880a(10) =2674a(11) =8284a(12) =26347a(13) =85076a(14) =279324a(15) =928043a(16) =3118915a(17) =10580145a(18) =36199094a(19) =124774041a(20) =432990333a(21) =1511628113a(22) =5306305978a(23) =18719781786a(24) =66342222729a(25) =236100395649a(26) =843490024052