perl -e'$"="";$x=pop;@x=reverse(1..$x);print " "x($x-$_),"@x[@x[1..$_]]@x[$x+1-$_..$x]\n"for@x[@x],@x' 9
         
        1
       121
      12321
     1234321
    123454321
   12345654321
  1234567654321
 123456787654321
12345678987654321
 123456787654321
  1234567654321
   12345654321
    123454321
     1234321
      12321
       121
        1