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 A046652 Triangle of rooted planar maps, read by rows. 2
 1, 2, 2, 3, 8, 7, 4, 21, 34, 30, 5, 44, 114, 160, 143, 6, 80, 308, 609, 806, 728, 7, 132, 715, 1908, 3315, 4256, 3876, 8, 203, 1482, 5185, 11420, 18444, 23256, 21318, 9, 296, 2814, 12600, 34520, 67856, 104652, 130416, 120175, 10, 414, 4984, 27965, 93924, 221300, 404016, 603801, 746350, 690690, 11, 560, 8343, 57584, 234066, 654336, 1394505, 2418372, 3533145, 4341480, 4032015 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 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 [Annotated scanned copy] EXAMPLE Triangle begins: 1; 2, 2; 3, 8, 7; 4, 21, 34, 30; 5, 44, 114, 160, 143; 6, 80, 308, 609, 806, 728; ... MAPLE T := proc(n, k) if k<=n then k*sum((2*j-k+1)*(j-1)!*(3*n-k-j)!/(j-k+1)!/(j-k)!/(2*k-j-1)!/(n-j)!, j=k..min(n, 2*k-1))/(2*n-k+1)! else 0 fi end: seq(seq(T(n, n-k+1), k=1..n), n=1..11); # Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 30 2008 MATHEMATICA t[n_, k_] := If[k <= n, k*Sum[(2*j-k+1)*(j-1)!*(3*n-k-j)!/(j-k+1)!/(j-k)!/(2*k-j-1)!/(n-j)!, {j, k, Min[n, 2*k-1]}]/(2*n-k+1)!, 0]; Table[t[n, k], {n, 1, 11}, {k, n, 1, -1}] // Flatten (* Jean-François Alcover, Jan 20 2014, after Herman Jamke *) CROSSREFS A091665 is the same triangle with rows reversed and has much more information. Sequence in context: A069830 A153935 A153944 * A319860 A300354 A091681 Adjacent sequences: A046649 A046650 A046651 * A046653 A046654 A046655 KEYWORD tabl,nonn,easy AUTHOR N. J. A. Sloane EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 30 2008 STATUS approved

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Last modified September 25 23:09 EDT 2023. Contains 365649 sequences. (Running on oeis4.)