This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A054515 Number of ways to place non-intersecting diagonals in convex (n+2)-gon so as to create no quadrilaterals. 1
 1, 2, 6, 21, 78, 301, 1198, 4888, 20340, 85986, 368239, 1594183, 6965380, 30675399, 136026759, 606848034, 2721783023, 12265670909, 55511013680, 252193872912, 1149742659556, 5258257323304, 24117924005616 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS L. Smiley, Generalization and some variants EXAMPLE a(3)=6 because the pentagon allows null placement and five ways to place two diagonals. MATHEMATICA InverseSeries[Series[(y-2*y^2+y^3-y^4)/(1-y), {y, 0, 24}], x] (* then A(x)=[y(x)-x]/x *) CROSSREFS A046736, A049124, A003168, A054514. Sequence in context: A124292 A129776 A129775 * A216490 A150190 A150191 Adjacent sequences:  A054512 A054513 A054514 * A054516 A054517 A054518 KEYWORD nonn AUTHOR Len Smiley (smiley(AT)math.uaa.alaska.edu), Apr 08 2000 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .