Let's go (once more)
I can't override the other explanation, so I added this here.
"iku" means "go".
"Ikou" is for "Let's go".
"Iku" is the common writing form.
But "iku" is often pronounced "yuku"
like "iu"(=say) is often pronouced "yuu".
Also "ikou" is pronouced "yukou".
^^ sourced from Yahoo Answers.