solve_inconsistent_error SciMax Toolbox solve_rec_rat

SciMax Toolbox >> solve_rec

solve_rec

Maxima Function

Calling Sequence

solve_rec (eqn, var, [init])

Description

Solves for hypergeometrical solutions to linear recurrence eqn with polynomials coefficient in variable var. Optional arguments init are initial conditions.

solve_rec can solve linear recurrences with constant coefficients, finds hypergeometrical solutions to homogeneous linear recurrences with polynomial coefficients, rational solutions to linear recurrences with polynomial coefficients and can solve Ricatti type recurrences.

Note that the running time of the algorithm used to find hypergeometrical solutions is exponential in the degree of the leading and trailing coefficient.

To use this function first load the solve_rec package with load(solve_rec);.

Example of linear recurrence with constant coefficients:

(%i2) solve_rec(a[n]=a[n-1]+a[n-2]+n/2^n, a[n]);
                        n          n
           (sqrt(5) - 1)  %k  (- 1)
                            1           n
(%o2) a  = ------------------------- - ----
       n               n                  n
                      2                5 2
                                                n
                                   (sqrt(5) + 1)  %k
                                                    2    2
                                 + ------------------ - ----
                                            n              n
                                           2            5 2

Example of linear recurrence with polynomial coefficients:

(%i7) 2*x*(x+1)*y[x] - (x^2+3*x-2)*y[x+1] + (x-1)*y[x+2];
                         2
(%o7) (x - 1) y      - (x  + 3 x - 2) y      + 2 x (x + 1) y
               x + 2                   x + 1                x
(%i8) solve_rec(%, y[x], y[1]=1, y[3]=3);
                              x
                           3 2    x!
(%o9)                 y  = ---- - --
                       x    4     2

Example of Ricatti type recurrence:

(%i2) x*y[x+1]*y[x] - y[x+1]/(x+2) + y[x]/(x-1) = 0;
                            y         y
                             x + 1     x
(%o2)         x y  y      - ------ + ----- = 0
                 x  x + 1   x + 2    x - 1
(%i3) solve_rec(%, y[x], y[3]=5)$
(%i4) ratsimp(minfactorial(factcomb(%)));
                                   3
                               30 x  - 30 x
(%o4) y  = - -------------------------------------------------
       x        6      5       4       3       2
             5 x  - 3 x  - 25 x  + 15 x  + 20 x  - 12 x - 1584

See also: , , and .

solve_inconsistent_error SciMax Toolbox solve_rec_rat