REcontent returns the content of the shift operator (that is, INFO[shifteqn]), thus returning the greatest common divisor of the coefficients of the operator.

Similarly, REprimpart returns INFO[shifteqn]/REcontent(problem). Note:  Whereas the sign is removed from the content, it is not removed from the primitive part.

$\mathrm{with}\left(\mathrm{LREtools}\right)\:$

$\mathrm{REcontent}\left(\left(n+1\right)u\left(n+2\right)+\left(n+1\right)u\left(n\right)\,u\left(n\right)\,\varnothing \right)$

$n+1$

$\mathrm{REprimpart}\left(\left(n+1\right)u\left(n+2\right)+\left(n+1\right)u\left(n\right)\,u\left(n\right)\,\varnothing \right)$

${{\mathrm{\&Shift}}_n\left(u\right)}^2+1$

$\mathrm{REcontent}\left(\left(n+1\right)u\left(n+2\right)+\left(n+2\right)u\left(n\right)\,u\left(n\right)\,\varnothing \right)$

$1$

$\mathrm{REprimpart}\left(\left(n+1\right)u\left(n+2\right)+\left(n+2\right)u\left(n\right)\,u\left(n\right)\,\varnothing \right)$

${{\mathrm{\&Shift}}_n\left(u\right)}^{2}n+{{\mathrm{\&Shift}}_n\left(u\right)}^2+n+2$