Number of disconnected 2-regular simple graphs on n vertices with girth at least 4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =1a(9) =1a(10) =2a(11) =2a(12) =4a(13) =4a(14) =6a(15) =7a(16) =10a(17) =11a(18) =15a(19) =17a(20) =23a(21) =26a(22) =33a(23) =38a(24) =49a(25) =56a(26) =69a(27) =80a(28) =99a(29) =114