Number of n-node graphs with no cycles of length less than 5.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =11a(5) =23a(6) =48a(7) =114a(8) =293a(9) =869a(10) =2963a(11) =12066a(12) =58933a(13) =347498a(14) =2455693a(15) =20592932a(16) =202724920a(17) =2322206466a(18) =30743624324a(19) =468026657815