Number of connected 4-regular simple graphs on n vertices with girth exactly 5.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =0a(11) =0a(12) =0a(13) =0a(14) =0a(15) =0a(16) =0a(17) =0a(18) =0a(19) =1a(20) =2a(21) =8a(22) =131a(23) =3917a(24) =123859a(25) =4131991a(26) =132160607a(27) =4018022149a(28) =118369811959