# Singular

#### D.14.1.28 arrEdelmanReiner

Procedure from library `arr.lib` (see arr_lib).

Usage:
arrEdelmanReiner();

Return:
the Edelman-Reiner arrangement, which is a free arrangement but the restriction to the 6-th hyperplane is nonfree.
(i.e. counterexample for Orlik-Conjecture)

Note:
the active ring must have at least five variables

Example:
 ```LIB "arr.lib"; ring r=0,x(1..5),dp; arrEdelmanReiner(); ==> _[1]=x(1) ==> _[2]=x(2) ==> _[3]=x(3) ==> _[4]=x(4) ==> _[5]=x(5) ==> _[6]=x(1)-x(2)-x(3)-x(4)-x(5) ==> _[7]=x(1)-x(2)-x(3)-x(4)+x(5) ==> _[8]=x(1)-x(2)-x(3)+x(4)-x(5) ==> _[9]=x(1)-x(2)-x(3)+x(4)+x(5) ==> _[10]=x(1)-x(2)+x(3)-x(4)-x(5) ==> _[11]=x(1)-x(2)+x(3)-x(4)+x(5) ==> _[12]=x(1)-x(2)+x(3)+x(4)-x(5) ==> _[13]=x(1)-x(2)+x(3)+x(4)+x(5) ==> _[14]=x(1)+x(2)-x(3)-x(4)-x(5) ==> _[15]=x(1)+x(2)-x(3)-x(4)+x(5) ==> _[16]=x(1)+x(2)-x(3)+x(4)-x(5) ==> _[17]=x(1)+x(2)-x(3)+x(4)+x(5) ==> _[18]=x(1)+x(2)+x(3)-x(4)-x(5) ==> _[19]=x(1)+x(2)+x(3)-x(4)+x(5) ==> _[20]=x(1)+x(2)+x(3)+x(4)-x(5) ==> _[21]=x(1)+x(2)+x(3)+x(4)+x(5) ==> ```