Number of matchings in the n-sun graph.

Terms

a(0) =1a(1) =3a(2) =8a(3) =27a(4) =100a(5) =393a(6) =1624a(7) =7017a(8) =31558a(9) =147177a(10) =709592a(11) =3527769a(12) =18045428a(13) =94797147a(14) =510594056a(15) =2815698483a(16) =15877236898a(17) =91442860467a(18) =537363872008