The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A045744 Number of noncrossing connected graphs on n nodes on a circle having no four-sided faces. 3
 1, 4, 22, 141, 988, 7337, 56749, 452332, 3689697, 30652931, 258465558, 2206330790, 19029531220, 165582392070, 1451789520435, 12813638048184, 113755675163767, 1015119850103821, 9100463691522759, 81923222827031025 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 2..200 FORMULA a(n) = Sum_{i=0..floor((n-2)/3)} binomial(n-2+i, i)*binomial(4*n-4-i, n-2-3*i)/(n-1). PROG (PARI) a(n) = if(n>1, sum(i=0, floor((n-2)/3), binomial(n-2+i, i)*binomial(4*n-4-i, n-2-3*i))/(n-1)); \\ Andrew Howroyd, Nov 12 2017 CROSSREFS Column k=0 of A094046. Cf. A045743. Sequence in context: A077056 A227404 A190271 * A243626 A104991 A027391 Adjacent sequences:  A045741 A045742 A045743 * A045745 A045746 A045747 KEYWORD nonn AUTHOR 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.

Last modified September 27 03:08 EDT 2020. Contains 337380 sequences. (Running on oeis4.)