The pesky rumor that Mayor Bloomberg wants to buy the New York Times just won’t go away. The multibillionaire isn’t ready to disappear after three terms as New York’s mayor, reports The Post’s Richard Johnson. “He’s going to need something grandiose that puts him on the national stage,” said a source, “and philanthropy won’t cut it.” Bloomberg — like fellow billionaires Bill Gates and Warren Buffett — is committed to giving away the bulk of his $25 billion fortune. He has also been aggressively growing his media company with acquisitions. “Bloomberg would consider the Times the ‘jewel in his crown’ after he relinquishes the mayoralty,” said our source. A Times spokeswoman told us: “The New York Times is not for sale.” But a veteran media watcher said, “That rumor has come around a few times. One of these days, it will be right.” Meanwhile, Donald Trump said on Fox Business Network of buzz that he’s looking to buy the Times: “I’ve looked at it . . . Their numbers are amazingly bad. They have a tremendous unfunded liability. I guess it’s over $1 billion . . . I look at everything. If something happens, it happens.” On the possibility of Times op-ed columnist Paul Krugman reporting to him, the mogul added, “That would be very interesting. That would be really a lot of fun . . . He might not be reporting for very long.”