A378076 Number of embeddings on the sphere of 2-connected homeomorphically irreducible planar graphs with n edges.

1, 0, 1, 2, 3, 6, 16, 37, 100, 293, 888, 2822, 9305, 31274, 106972, 370828, 1298058, 4582413, 16289759, 58259600, 209465186

Offset: 6

Author

Andrew Howroyd, Nov 15 2024

Keywords

• nonn
• more

Comments

Homeomorphically irreducible means each vertex has a degree of at least 3.

Crossrefs

Antidiagonal sums of A378075.

Cf. A002840, A006407, A187928.

Formula

a(n) = A002840(n) + A187928(n).

a(n) = Sum_{k=4..n-2} A378075(k, n+2-k).