A047009 T(2n,n), array T given by A047000.

1, 2, 4, 14, 60, 286, 1456, 7752, 42636, 240350, 1381380, 8064030, 47682960, 284997384, 1719031840, 10450528048, 63967345068, 393895175646, 2438398706380, 15166284983850, 94730949283740, 593966352738990

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Comments

Also: number of nonseparable planar rooted maps with n edges. - R. J. Mathar, Aug 18 2006

Links

• T. R. S. Walsh, A. B. Lehman, Counting rooted maps by genus. III: Nonseparable maps, J. Combinatorial Theory Ser. B 18 (1975), 222-259.

Formula

a(n) = 2*A006013(n-1) = 2*(3n-2)!/(n!*(2*n-1)!). - R. J. Mathar, Aug 18 2006

G.f.: 1+2*g where g*(1-g)^2 = x. - Mark van Hoeij, Nov 10 2011