$ for i in `seq 1 40` ; do ./something $i ; done
$ for i in $(seq 1 40) ; do ./something $i ; done

seq is nice for that, but the syntax feels a bit hard to type. If you don't need sh compatibility (read: in bash/zsh), try:

$ for i in {1..40} ; do ./something $i ; done

PS: no spaces allowed

PS 2: another useful feature is prefixes/suffixes as in "touch {1..40}.txt"