login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A058050 a(n) is the number of different graphs drawn in the following way: you decide for each number k <= n on a pair of positive numbers (x(k),y(k)) such that x(k)+y(k)=k; you draw n points numbered 1 to n; draw two arrows from n, one to x(n) and one to y(n); draw two arrows from each k already reached by an arrow, one to x(k) and one to y(k). The process stops when 1 is the only point reached by an arrow without any arrow leaving it; you can also erase the isolated points. 0
1, 1, 1, 2, 3, 6, 11, 22, 43, 87, 176, 357, 732, 1497, 3089, 6335, 13099, 26956, 55779, 114904, 237734, 490096, 1013276, 2089105, 4315487, 8894624, 18356468, 37813944, 77958972, 160487953, 330533009, 679920989, 1398944724, 2875374720, 5910355198, 12138248459, 24927057132, 51151600936 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
LINKS
Sean A. Irvine, Java program (github)
EXAMPLE
a(5)=3: there are two possibilities to cut 5, i.e., (1,4) and (2,3); (1,4) gives two possibilities to draw such a graph because 4 also has two ways of cutting: (2,2) and (1,4); (2,3) gives one possibility; and 2+1=3.
CROSSREFS
Sequence in context: A043327 A247968 A005578 * A026418 A063895 A337090
KEYWORD
nonn
AUTHOR
Mathieu Dupont (mathieudupont(AT)usa.net), Nov 18 2000
EXTENSIONS
More terms from Sean A. Irvine, Jul 21 2022
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)