RSolve

RSolve[eqn,a[n],n] solves a recurrence equation for a[n]. 

RSolve[{eqn1,eqn2,…},{a1[n],a2[n],…},n] solves a system of recurrence equations. 

RSolve[eqn,a[n1,n2,…],{n1,n2,…}] solves a partial recurrence equation. 

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