On platforms without seq (MacOSX, Solaris), you can emulate it using dc as follows (note the upper bound and the lower bound):
echo '[1+pdupper bound>aq]salower bound 1-lax' | dc
For example:
alia:~ andrea$ echo '[1+pd5>aq]sa0 1-lax' | dc
0
1
2
3
4
5
alia:~ andrea$
