Give a recursive definition for the set X of all natural numbers that are one or two more than a multiple of $10.$ In other words, give a recursive definition for the set $\{1,2,11,12,21,22,31,32,...\}.$

B$1.1$ is in X$.$

B$2.$

is in X$.$

R$.$ If

x is in X$,$

so is

$.$