For purposes of paragraph (1), a corporation shall be treated as a controlled corporation if, at any time after the transfer of the property and during the 3-year period ending on the date of the decedent’s death, the decedent owned (with the application of section
318), or had the right (either alone or in conjunction with any person) to vote, stock possessing at least 20 percent of the total combined voting power of all classes of stock.