Permutaion - Combination

  n =   1 30       r =   0 30
[Permutation]
\(n !\) =   \(r !\) =  
      \({}_n {P}_{r}\) =   (Non-replacement)   \(r \le n\)
\({}_n {Π}_{r}\) =   (Replacement)
[Combination]
      \({}_n {C}_{r}\) =   (Non-replacement)  \( r \le n\)
  \({}_n {H}_{r}\) =   (Replacement)  \({}_{n+r-1} C_{r} \)
[Permutation with the same thing]
      n = \(= p + q + r + s\)       p = q = r = s =
        \(\frac{n!}{p!\, q! \, r! \, s!}\) =
   *** \(\;\; {}_n P_{2},\; {}_n C_{2} \;\;\) \( \; n ≤ 10\)