221724

Appears in sequences

• Triangle read by rows: numbers of isomers of unbranched a-4-catapolynonagons.at n=46A120650
• Unbranched a-4-catapolynonagons (see Brunvoll reference for precise definition).at n=7A121124
• G.f. satisfies A(x)/A(x^2) = (1 + 9x + 9x^2 + 9x^3 + ...).at n=28A176201