a(n) is the number of nonseparable planar maps with 2*n+1 edges and a fixed outer face of 4 edges which are invariant under a rotation of a 1/2 turn. (Column 2 of A091665.)
A046649
a(n) is the number of nonseparable planar maps with 2*n+1 edges and a fixed outer face of 4 edges which are invariant under a rotation of a 1/2 turn. (Column 2 of A091665.)
Terms
- a(0) =2a(1) =8a(2) =34a(3) =160a(4) =806a(5) =4256a(6) =23256a(7) =130416a(8) =746350a(9) =4341480a(10) =25594530a(11) =152585472a(12) =918324904a(13) =5572034240a(14) =34048494608a(15) =209347674768
External references
- oeis: A046649