OFFSET
0,1
LINKS
S. Kitaev, P. Salimov, C. Severs and H. Ulfarsson, Restricted non-separable planar maps and some pattern avoiding permutations, 2012.
S. Kitaev, P. Salimov, C. Severs and H. Ulfarsson, Restricted non-separable planar maps and some pattern avoiding permutations, Discrete Applied Mathematics, Volume 161, Issues 16-17, November 2013, Pages 2514-2526.
FORMULA
G.f.: A(x/(1+x)), where A(x) is g.f. for A000139.
Conjecture: 2*(n+1)*(2*n+1)*a(n) +(-15*n^2+19*n-8)*a(n-1) -2*(21*n-22)*(n-2)*a(n-2) -23*(n-2)*(n-3)*a(n-3)=0. - R. J. Mathar, May 30 2014
a(n) ~ 23^(n + 3/2) / (81 * sqrt(Pi) * n^(5/2) * 2^(2*n+1)). - Vaclav Kotesovec, Apr 27 2024
MATHEMATICA
A[x_] = (2/(3x)) (HypergeometricPFQ[{-2/3, -1/3}, {1/2}, (27/4) x] - 1);
A[x/(1+x)] + O[x]^29 // CoefficientList[#, x]& (* Jean-François Alcover, Aug 29 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 01 2013
STATUS
approved