Bash

Convert between numerical bases
printf "hex2dec=";echo "ibase=16;$1"|bc printf "dec2hex=";echo "obase=16;$1"|bc printf "oct2dec=";echo "ibase=8;$1"|bc printf "dec2oct=";echo "obase=8;$1"|bc
 * 1) !/bin/bash

Print primes between any two numbers
for (( i=$1; i<=$2; i++ ));do l=$(factor $i | cut -d : -f 1) r=$(factor $i | cut -d : -f 2 | sed 's/ //g') if (( $l == $r ));then echo $i fi done
 * 1) !/bin/bash