correct test to see if function of summation variable
correct test to see if function of summation variable

kaushik94/sympy,jaimahajan1997/sympy,skidzo/sympy,aktech/sympy,madan96/sympy,chaffra/sympy,chaffra/sympy,skidzo/sympy,madan96/sympy,yashsharan/sympy,yashsharan/sympy,aktech/sympy,souravsingh/sympy,madan96/sympy,yashsharan/sympy,souravsingh/sympy,jaimahajan1997/sympy,aktech/sympy,skidzo/sympy,jaimahajan1997/sympy,souravsingh/sympy,kaushik94/sympy,chaffra/sympy,kaushik94/sympy