I want to do some stuff with symbolic arrays like this
a[[j]] + a[[j + 1]] == a[[j - 1]] + a[[j - 2]]
But upon declaring such an expression I get
Part::pkspec1: The expression j cannot be used as a part specification.
for all indices in the expression. It also does not work with the above expression when, for example, putting it into solve.
How can I do symbolic math with smybolic arrays?
Solve[a[[j]] + a[[j + 1]] == a[[j - 1]] + a[[j - 2]], a[[j]]]