OFFSET
0,2
COMMENTS
The number of rooted isthmusless n-edge maps in the plane (planar with a distinguished outside face). - Valery A. Liskovets, Mar 17 2005
REFERENCES
L. M. Koganov, V. A. Liskovets, T. R. S. Walsh, Total vertex enumeration in rooted planar maps, Ars Combin. 54 (2000), 149-160.
V. A. Liskovets and T. R. Walsh, Enumeration of unrooted maps on the plane, Rapport technique, UQAM, No. 2005-01, Montreal, Canada, 2005.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..500
V. A. Liskovets and T. R. Walsh, Counting unrooted maps on the plane, Advances in Applied Math., 36, No.4 (2006), 364-387.
FORMULA
a(n) = 12*n*(4*n-1)!*(5*n^2+13*n+2)/(n!*(3*n+3)!) for n > 0.
G.f.: -(1-3*g+g^2)*g where g = 1+x*g^4 is the g.f. of A002293. - Mark van Hoeij, Nov 11 2011
a(n) = Sum_{k=1..n+1} k*A342981(n, k). - Andrew Howroyd, Apr 06 2021
MAPLE
12*n*(4*n-1)!*(5*n^2+13*n+2)/(n!*(3*n+3)!);
MATHEMATICA
Join[{1}, Table[12n (4n-1)! (5n^2+13n+2)/(n!(3n+3)!), {n, 20}]] (* Harvey P. Dale, May 20 2018 *)
PROG
(PARI) a(n) = if(n==0, 1, 12*n*(4*n-1)!*(5*n^2+13*n+2)/(n!*(3*n+3)!)) \\ Andrew Howroyd, Apr 06 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Offset corrected and terms a(21) and beyond from Andrew Howroyd, Apr 06 2021
STATUS
approved