A242638 Number of quadrangulations of a hexagon b_1 w_3 b_2 w_1 b_3 w_2 having n inner faces and not containing the edge b_1 w_1.

0, 0, 2, 10, 47, 226, 1122, 5738, 30107, 161460, 882180, 4897752, 27570532, 157083944, 904523386, 5257488138, 30814928707, 181966070440, 1081790956890, 6470568865530, 38917734372615, 235260687007290, 1428777440333880, 8714285083290072, 53359037547384852

Offset

0,3

Links

Andrew Howroyd, Table of n, a(n) for n = 0..500

Sergey Kitaev, Anna de Mier, Marc Noy, On the number of self-dual rooted maps, European J. Combin. 35, 2014, pp377-387, MR3090510.

Formula

G.f.: (2 - 6*g(x) + 3*g(x)^2)*g(x)^2/(1 - g(x))^4 where g(x)/x is the g.f. of A006013. - Andrew Howroyd, Feb 23 2020

Prog

(PARI) seq(n)={my(g=serreverse(x*(1-x)^2 + O(x^n))); Vec((2 - 6*g + 3*g^2)*g^2/(1 - g)^4, -(n+1))} \\ Andrew Howroyd, Feb 23 2020

Crossrefs

Cf. A006013, A242637.

Sequence in context: A321274 A166107 A034429 * A058149 A009314 A009316

Adjacent sequences: A242635 A242636 A242637 * A242639 A242640 A242641

Keyword

nonn

Author

N. J. A. Sloane, May 19 2014

Extensions

Terms a(6) and beyond from Andrew Howroyd, Feb 23 2020

Status

approved