login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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-Fran├žois 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)