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The LREtools package contains commands to manipulate and find certain types of solutions of Linear Recurrence Equations.

The name LRETools can be used as a synonym for LREtools.

Each command in the LREtools package can be accessed by using either the long form or the short form of the command name in the command calling sequence.

The following is a list of available commands.

To display the help page for a particular LREtools command, see Getting Help with a Command in a Package .

The following is a list of available subpackages.

$\mathrm{LREtools}\left[\mathrm{REtodelta}\right]\left(u\left(n+2\right)-2u\left(n+1\right)+u\left(n\right)\,u\left(n\right)\,\varnothing \right)$

${\left(\mathrm{LREtools}\left[\mathrm{\Delta }\right]\right)}_n^2$

$\mathrm{rec}≔a\left(n+2\right)-\frac{\left(2n+1\right)a\left(n+1\right)}{n}+\frac{na\left(n\right)}{n-1}=n\left(n+1\right)\:$

$\mathrm{re}≔\mathrm{LREtools}\left[\mathrm{REcreate}\right]\left(\mathrm{rec}\,a\left(n\right)\,\varnothing \right)$

$\mathrm{re}≔\mathrm{RESol}\left(\left\{n^{2}a\left(n\right)+\left(-2n^2+n+1\right)a\left(n+1\right)+\left(n^2-n\right)a\left(n+2\right)=n^2\left(n-1\right)\left(n+1\right)\right\}\,\left\{a\left(n\right)\right\}\,\left\{a\left(1\right)=0\,a\left(2\right)=a\left(2\right)\,a\left(3\right)=a\left(3\right)\right\}\,\mathrm{INFO}\right)$

$\mathrm{LREtools}\left[\mathrm{polysols}\right]\left(\mathrm{re}\,\mathrm{output}=\mathrm{basis}\right)$

$\left[\left[n-1\right]\,\frac{1}{9}{n}^4-\frac{5}{18}{n}^3-\frac{1}{9}{n}^2+\frac{5}{18}\right]$

$f≔\mathrm{LREtools}\left[\mathrm{REtoproc}\right]\left(\left(1-n^2\right)u\left(n+1\right)+\frac{3}{2}u\left(n-1\right)+\left(\frac{1}{2}+\frac{3}{2}n+n^2\right)u\left(n\right)\,u\left(n\right)\,\left\{u\left(0\right)=1\,u\left(2\right)=a\right\}\right)$

$f≔\mathbf{proc}\left(n::\mathrm{nonnegint}\,\$\right)\mathbf{local}i\,\mathrm{u0}\,\mathrm{u1}\,\mathrm{u2}\;\mathrm{u0}≔\−1\/2\;\mathrm{u1}≔a\;\mathbf{if}n\=1\mathbf{then}\mathrm{u0}\mathbf{elif}n\=2\mathbf{then}\mathrm{u1}\mathbf{else}\mathbf{for}i\mathbf{from}3\mathbf{to}n-1\mathbf{do}\mathrm{u2}≔\−\left(3\*\mathrm{u0}\+\left(2\*\mathrm{u1}\*i-\mathrm{u1}\right)\*i\right)\/\left(\left(4-2\*i\right)\*i\right)\;\mathrm{u0}≔\mathrm{u1}\;\mathrm{u1}≔\mathrm{u2}\mathbf{end\; do}\;\−\left(3\*\mathrm{u0}\+\left(2\*\mathrm{u1}\*n-\mathrm{u1}\right)\*n\right)\/\left(\left(\−2\*n\+4\right)\*n\right)\mathbf{end\; if}\mathbf{end\; proc}$

$f\left(10\right)$

$\frac{86773903a}{3440640}-\frac{41665019}{17203200}$

$\mathrm{LREtools}\left[\mathrm{REtoDE}\right]\left(\left(18+12n\right)t\left(n\right)+\left(-20-7n\right)t\left(n+1\right)+\left(4+n\right)t\left(n+2\right)\,t\left(n\right)\,\left\{t\left(0\right)=0\,t\left(1\right)=2\right\}\,y\left(z\right)\right)$

$\mathrm{DESol}\left(\left\{\left(-18z^2+13z-2\right)y+\left(-12z^3+7z^2-z\right)\mathrm{D}\left(y\right)+6z\right\}\,\left\{y\right\}\,\left\{y\left(0\right)=0\,\mathrm{D}\left(y\right)\left(0\right)=2\right\}\right)$