let n be odd Nat; :: thesis: ( not n <= 6 or n = 1 or n = 3 or n = 5 )
assume A1: n <= 6 ; :: thesis: ( n = 1 or n = 3 or n = 5 )
n <> 2 * 3 ;
then n < 5 + 1 by A1, XXREAL_0:1;
then A2: n <= 5 by NAT_1:13;

per cases ( n = 5 or n < 4 + 1 ) by A2, XXREAL_0:1;

suppose n = 5 ; :: thesis: ( n = 1 or n = 3 or n = 5 )

hence ( n = 1 or n = 3 or n = 5 ) ; :: thesis: verum

end;

suppose n < 4 + 1 ; :: thesis: ( n = 1 or n = 3 or n = 5 )

then n <= 4 by NAT_1:13;
hence ( n = 1 or n = 3 or n = 5 ) by Th7; :: thesis: verum

end;

end;