Number of unrooted planar 2-constellations with n digons. Also number of n-edge unrooted planar Eulerian maps with bicolored faces.

A090371

Number of unrooted planar 2-constellations with n digons. Also number of n-edge unrooted planar Eulerian maps with bicolored faces.

Terms

    a(0) =1a(1) =3a(2) =6a(3) =20a(4) =60a(5) =291a(6) =1310a(7) =6975a(8) =37746a(9) =215602a(10) =1262874a(11) =7611156a(12) =46814132a(13) =293447817a(14) =1868710728a(15) =12068905911a(16) =78913940784a(17) =521709872895

External references