not quite optimized since you're still calling $gettok() and $numtok() many more times than necessary - set them to local variables if you're sure their values won't change across multiple calls. not to mention the method is slow in and of itself :P

a quick method for calculating the LCM of a list of integers is to note that LCM(a, b, c, ...) = LCM(LCM(a, b), c, ...), and that LCM(a, b) = a * b / GCD(a, b) where GCD() is the greatest common divisor and can be found using a very simple algorithm:

alias gcd {
  while ($2) tokenize 32 $2 $calc($1 % $2)
  return $1
} 

then $lcm() can be defined as:

alias lcm {
  var %i = 2, %lcm = $gettok($1, 1, 32)
  while ($gettok($1, %i, 32) != $null) {
    %lcm = $lcm_($v1, %lcm)
    inc %i
  }
  return %lcm
}

alias lcm_ {
  return $calc($1 * $2 / $gcd($1, $2))
}

where $lcm_() calculates the LCM of a pair of integers.

this is much more optimal and even lets you do away with requiring a value for $2, which shouldn't be necessary.