pack(n,v) -- packs the elements of the list or sequence v into a table n at a time.
It produces, from a list v, a list of lists formed by packing the elements of v into lists n at a time. The last of the lists produced may have fewer than n elements.
i1 : pack(3,{a,b,c,d,e,f,g,h,i,j,k})
o1 = {{a, b, c}, {d, e, f}, {g, h, i}, {j, k}}
o1 : List