PROGRAM:TOHSOLVE
Repeat A>=1 and A<=16
Input "NO. OF RINGS? ",A
End
List>matr(seq(R,R,1,A),[C]
{A+1,3->dim([C]
[[1,2][1,3][2,3->[E]
A+1
{1,Ans,Ans->L1
Delvar R Clrhome
"ABCDEFGHIJKLMNOP->Str0
Disp sub(Ans,1,A
For(M,2,2^A
R+1-R(R=3->R
[E](Ans,2
[C](L1(Ans),Ans->J
[E](R,1
[C](L1(Ans),Ans
J and J<Ans or not(Ans ->J
[E](R,Ans+1->B
L1(Ans->I
Output(B,Ans," \\One space
[C](Ans,B->C
I+1->L1(B
[E](R,2-J ->B
L1(Ans ->I
C->[C](Ans-1,B
I-1->L1(B
Output(B,Ans,sub(Str0,C,1
End
310 bytes.