*HEADING
: EIGENVALUE ANALYSIS OF AN UNCONSTRAINED 1-ELEMENT MESH  [MCL6]
*NODE,NSET=NALL
1,1.,0.,0.
2,0.707106781,0.707106781,0.
3,0.,1.,0.
4,1.,0.,1.
5,0.707106781,0.707106781,1.
6,0.,1.,1.
*ELEMENT,TYPE=MCL6,ELSET=ONE
1,1,4,6,3,5,2
*MEMBRANE SECTION,ELSET=ONE,MATERIAL=MONE
0.1
*MATERIAL,NAME=MONE
*ELASTIC
3.E6,.3
*DENSITY
7.5E-4,
*STEP
*FREQUENCY, EIGENSOLVER=LANCZOS, SIM=NO
12, , ,-1.E7 
*OUTPUT,HISTORY,FREQUENCY=1
*MODAL OUTPUT
*END STEP