Task: Question Answering
Input (English): Question: To calculate the number of different genotypes in any allelic series the formula is applied: 
 Options:  <1> (n-1) / 2. <2> n x (n + 1) / 2. <3> n x (n-1) / 2. <4> (n-1) x (n + 1) / 2. <5> (2n-1) / 2.
Output (English): 2