Number of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is oriented, the sphere is not oriented (OU case).
A007756
Number of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is oriented, the sphere is not oriented (OU case).
Terms
- a(0) =0a(1) =0a(2) =1a(3) =1a(4) =2a(5) =3a(6) =11a(7) =38a(8) =156a(9) =638a(10) =2973a(11) =13882a(12) =67868a(13) =338147a(14) =1720303a(15) =8905996a(16) =46774728a(17) =248918004a(18) =1340083514a(19) =7288922610a(20) =40019870539a(21) =221582395052
External references
- oeis: A007756