OFFSET
1,7
LINKS
Gheorghe Coserea, Table of n, a(n) for n = 1..107 (corrected by Georg Fischer, Jan 20 2019)
Mednykh, A.; Nedela, R. Recent progress in enumeration of hypermaps, J. Math. Sci., New York 226, No. 5, 635-654 (2017) and Zap. Nauchn. Semin. POMI 446, 139-164 (2016), table 5
Timothy R. Walsh, Space-Efficient Generation of Nonisomorphic Maps and Hypermaps
Timothy R. Walsh, Space-Efficient Generation of Nonisomorphic Maps and Hypermaps, J. Int. Seq. 18 (2015) # 15.4.3.
Peter G. Zograf, Enumeration of Grothendieck's Dessins and KP Hierarchy, International Mathematics Research Notices, Volume 2015, Issue 24, 1 January 2015, 13533-13544.
Peter G. Zograf, Enumeration of Grothendieck's Dessins and KP Hierarchy, arXiv:1312.2538 [math.CO], 2014.
FORMULA
G.f.: y*(y - 1)^7*(5*y^9 - 60*y^8 + 675*y^7 - 2947*y^6 + 10005*y^5 - 20235*y^4 + 28297*y^3 - 23937*y^2 + 11418*y - 1781)/(2*(y - 2)^12*(y + 1)^9), where y = C(2*x), C being the g.f. for A000108. - Gheorghe Coserea, Nov 12 2018
MATHEMATICA
DeleteCases[CoefficientList[Series[# (# - 1)^7*(5 #^9 - 60 #^8 + 675 #^7 - 2947 #^6 + 10005 #^5 - 20235 #^4 + 28297 #^3 - 23937 #^2 + 11418 # - 1781)/(2 (# - 2)^12*(# + 1)^9) &[(1 - Sqrt[1 - 8 x])/(4 x)], {x, 0, 23}], x], 0] (* Michael De Vlieger, Nov 26 2018 *)
PROG
(PARI)
seq(N) = {
my(x='x+O('x^(N+2)), y=(1-sqrt(1-8*x))/(4*x));
Vec(y*(y - 1)^7*(5*y^9 - 60*y^8 + 675*y^7 - 2947*y^6 + 10005*y^5 - 20235*y^4 + 28297*y^3 - 23937*y^2 + 11418*y - 1781)/(2*(y - 2)^12*(y + 1)^9));
};
seq(18) \\ Gheorghe Coserea, Nov 12 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 01 2012
EXTENSIONS
a(13)-a(14) by Noam Zeilberger, Sep 16 2018
More terms from Gheorghe Coserea, Nov 11 2018
STATUS
approved