$2\mathrm{.}4$ Create the following secquences:

$1."$a$","$a$","$a$","$a$","$a$"$

$2.1,3...\mathrm{.}99($the odd numbers in $|1,100$

$|)$

$3.1,1,1,2,2,2,3,3,3$

$4.1,1,1,2,2,3,$

$5.1,2,3,4,5,4,3,2,1$

using : $,$ seq or rep as appropriate.