SAN FRANCISCO - Rapidly growing online-coupon-seller Groupon Inc. is dangling its most tantalizing deal yet - an initial public offering of stock.

The prospect is likely to intensify a debate about whether an investment bubble is forming around promising but still unproven Internet companies.

Groupon took the first step toward selling its stock on Wall Street by filing its IPO papers Wednesday with the Securities and Exchange Commission. The much-anticipated filing comes just two weeks after LinkedIn Corp., a popular Internet service for professional networking, saw its shares double in their first day of trading. That surge evoked memories of the early stages of the dot-com boom in the 1990s.

Groupon, based in Chicago, offers its subscribers the chance to purchase daily discounts targeted to their city and preferences. For example, a subscriber might pay $20 for a $40 gift certificate to a spa, restaurant, car wash or yoga studio.

The initial price of Groupon's shares and the number of shares won't be set until the company gets closer to going public. That process typically takes three to four months.

But the shares won't be cheap, based on the confidence that Groupon showed last year when it rejected a $6 billion takeover offer from Internet search-leader Google Inc. Groupon said in its filing it hopes to raise up to $750 million in the IPO, but that figure often changes as investment bankers get better idea of the demand for the stock.

Several Internet companies are getting ready to dangle their stocks in front of investors hoping to get rich off the next big thing. Zynga, the maker of popular Web games such as FarmVille, could be next in the IPO line, with plenty of others such as online message service Twitter waiting in the wings.

Groupon's filing indicated some of the company's early investors intend to sell some of their holdings in the IPO but didn't provide further details.