`seq 4e4000003 4e4000003` is causing an infinite loop

Looking at seq oss fuzz coverage, I noticed that it wasn't producing much.
Writing a fuzz on seq parse number, i noticed that:
`cargo run seq  4e4000003 4e4000003`
is running forever

while GNU is doing:
```
$ LANG=C /usr/bin/seq 4e4000003 4e4000003
/usr/bin/seq: invalid floating point argument: '4e4000003'
```