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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A146558 Number of order n permutations without collinear triples modulo n. 1
1, 2, 0, 16, 0, 72, 0, 256, 0, 0, 0, 2304, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..13.

L. Li, Collinear triples in permutations, arXiv:0802.0572

FORMULA

For prime p>=3, a(p) = 0.

EXAMPLE

For n=4, there are a(4)=16 permutations without collinear triples: [1, 2, 4, 3], [1, 3, 2, 4], [1, 3, 4, 2], [1, 4, 2, 3], [2, 1, 3, 4], [2, 3, 1, 4], [2, 4, 1, 3], [2, 4, 3, 1], [3, 1, 2, 4], [3, 1, 4, 2], [3, 2, 4, 1], [3, 4, 2, 1], [4, 1, 3, 2], [4, 2, 1, 3], [4, 2, 3, 1], [4, 3, 1, 2]

PROG

(PARI) { a(n) = local(p, r, g); r=0; for(j=1, n!, p=numtoperm(n, j); g=1; forvec(v=vector(3, i, [1, n]), if(matdet([1, v[1], p[v[1]]; 1, v[2], p[v[2]]; 1, v[3], p[v[3]]])%n==0, g=0; break), 2); if(g, r++)); r }

CROSSREFS

Cf. A135538, A146557.

Sequence in context: A074031 A086261 A111978 * A025600 A009006 A155585

Adjacent sequences:  A146555 A146556 A146557 * A146559 A146560 A146561

KEYWORD

hard,more,nonn

AUTHOR

Max Alekseyev, Nov 01 2008

EXTENSIONS

Edited by Max Alekseyev, Jun 21 2010

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified June 25 20:26 EDT 2017. Contains 288730 sequences.