cat -n with different format?

[Peng Yu]

Hi,

I want to change how the line number is displayed

~$ echo a | cat -n
     1  a

For example, I want it to be shown as

1:a

Although this can be easily done in anything other scripting language,
I'm wondering if there is an even easier way to get it done with cat.

-- 
Regards,
Peng