Number of hex trees with n edges and no adjacent vertices of outdegree 2.

A126189

Number of hex trees with n edges and no adjacent vertices of outdegree 2.

Terms

    a(0) =1a(1) =3a(2) =10a(3) =36a(4) =135a(5) =519a(6) =2034a(7) =8100a(8) =32688a(9) =133380a(10) =549342a(11) =2280690a(12) =9534591a(13) =40103019a(14) =169583382a(15) =720549432a(16) =3074694552a(17) =13170845916a(18) =56616211818a(19) =244144402182

External references