Quasi-shuffle products playground

The following is a simple implementation of some quasi-shuffle products introduced in the course "Multiple zeta values and modular forms". This tool evaluates algebraic expressions of indices with certain quasi-shuffle products. 

• Input: Index $(k_1,\dots,k_r)$ = [$k_1,\dots,k_r$], Stuffle product = st, Shuffle product = sh,  double shuffle (sh - st) = ds, Stuffle product for $g(k_1,\dots,k_r)$ = gst
• Output: Linear combination of indices written as $(k_1,\dots,k_r)$.

Example:  [2] st [3] gives the output (2,3) + (3,2) + (5)
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[2] st [3]