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A046651 Triangle of rooted planar maps. 4
1, 1, 2, 1, 6, 6, 1, 12, 26, 24, 1, 20, 75, 120, 110, 1, 30, 174, 416, 594, 546, 1, 42, 350, 1176, 2289, 3094, 2856, 1, 56, 636, 2880, 7322, 12768, 16728, 15504, 1, 72, 1071, 6324, 20475, 44388, 72420, 93024, 86526, 1, 90, 1700, 12740, 51495, 136252, 267240, 417240, 528770, 493350, 1, 110, 2574, 23936, 118734, 378444, 878460, 1610136, 2437149, 3058770, 2861430 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..65.

W. G. Brown, Enumeration of non-separable planar maps, Canad. J. Math., 15 (1963), 526-545.

W. G. Brown, Enumeration of non-separable planar maps

MAPLE

T := proc(n, k) if k<=n then k*sum((2*j-k)*(j-1)!*(3*n-j-k-1)!/(j-k)!/(j-k)!/(2*k-j)!/(n-j)!, j=k..min(n, 2*k))/(2*n-k)! else 0 fi end: seq(seq(T(n, n-k+1), k=1..n), n=1..11); - Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 19 2008

MATHEMATICA

t[n_, k_] := If[k <= n, k*Sum[(2*j-k)*(j-1)!*(3*n-j-k-1)!/(j-k)!/(j-k)!/(2*k-j)!/(n-j)!, {j, k, Min[n, 2*k]}]/(2*n-k)!, 0]; Table[Table[t[n, n-k+1], {k, 1, n}], {n, 1, 11}] // Flatten (* Jean-Fran├žois Alcover, Jan 14 2014, after Herman Jamke *)

CROSSREFS

A091599 is the same triangle with rows reversed and has much more information.

Sequence in context: A259477 A208919 A259569 * A063007 A202190 A089231

Adjacent sequences:  A046648 A046649 A046650 * A046652 A046653 A046654

KEYWORD

tabl,nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 19 2008

STATUS

approved

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Last modified November 14 10:04 EST 2019. Contains 329111 sequences. (Running on oeis4.)