bash - GNU parallel with variable sequence? -

i want run program prog in parallel using gnu's parallel, argument takes value in sequence. example:

parallel prog ::: {1..100} 

however, don't know upper bound of sequence in advance, able like:

parallel prog ::: {1..$x} 

where $x number i'll compute somewhere. how can achieve this?

assuming seq program (or it) available,

parallel prog ::: $(seq 1 $x) 

if not, can fake it:

parallel prog ::: $(for ((i=1; < x; i++)) do; echo $i; done) 

as ole points out, if $x large, resulting sequence of numbers may large fit on command line. in case, use either of 2 methods above feed arguments parallel via standard input:

seq 1 "$x" | parallel prog ((i=1; i<x; i++)) do; echo "$i"; done | parallel prog