Forty-five minutes before the start of ceremonies opening the Olympic Games that America has shunned, a cheer went up in the 103,000-seat Lenin Central Stadium. A sandy-haired young man and an old gent in a greek fisherman's cap were waving the Stars and Stripes.

It was the only time the U.S. Flag would be displayed here today, and the Soviet crowd responded spontaneously. The cheers swelled, and applause filled the massive arena.

The young man, who brought Old Glory to Moscow in his suitcase but never imagined it would cause such a reaction, is a 22-year-old merchant seaman from Howard, Ohio, named Dan Patterson.

A thoughtful fellow making his first trip abroad, he said "I wanted to do this because I'm proud of my country. I'm here, even if our athletes aren't, and America is here. I'm proud to let the world know it."

His accomplice was 88-year-old Nick Paul of Astoria, N.Y., who was present at the first modern Olympics, in 1896 in his native Greece. He was 5 years old at the Athens Games, and has attended every Olympiad since, with the exception of the notorious "Nazi Olympics" in Berlin in 1936 ("I didn't go because of the political situation there"), and Rome in 1960.

"I do exercises every morning, so I was in good shape to hold up the flag," said Paul, who immigrated to the U.S. in 1920 and became an American citizen. A retired chef -- "I worked in all the big hotels, yeh, the Plaza, too," he said. He started making plans to attend the Moscow Games as soon as the site was announced six years ago, and wasn't going to let the U.S. boycott stop him.

"Tell Carter we're here despite him," said the spunky old man, who disagrees vehemently with the president's decision to boycott the Games because of the Soviet invastion of Afghanistan. "It's very sad that our athletes aren't here . . . we understand that it's not Carter so much as his advisers, but the advisers got it wrong."

Patterson and Paul are part of a group of 23 American tourists who plunked down $2,042 apiece to the New York-based Russian Travel Bureau for a 22-day trip to the Soviet Union, including six days at the Moscow Games.

Originally, 20,000 U.S. tourists contracted for similar packages, but about 90 percent of them canceled because of the boycott. Best estimates now are that between 1,500 and 2,000 Americans will visit the Moscow Games before they end Aug. 3.

Unaware of the controversy that has flared for several days between the U.S. government and the International Olympic Committee over White House objections to the use of the American flag in any connection with the Moscow Games, Patterson and Paul unfurled Old Glory at their seats in section 4 on the south side of Lenin Stadium, and thus became a footnote of Olympic history.

"No, I didn't expect to get the response I did," said the boyish-looking Patterson, who works for a steel company on a ship on the Great Lakes. "It felt good. In fact, it felt great."

The flag means different things to different people. To Patterson, it means the right to travel freely, a privilege that very few Soviet citizens enjoy, and to express his opinions and even to disagree publicly with his president.

"I respect President Carter, but I don't agree with everything he does," he said. "I'm sorry American athletes aren't here. I think the whole world is sorry, too. The athletes worked so hard to reach Olympic caliber.

"I don't agree with the boycott. I think he's using the athletes as a tool to accomplish something in foreign affairs, and that's not right.

"It's like a chess game, and he's using other people's lives, moving them around as pawns to accomplish his goals. I heard that he plans to invite the U.S. Olympians to the White House and give them each a medal. I think that's a bunch of baloney. You can't replace an Olympic medal just like that. Those medals won't mean a thing, not to me."

Paul was even more critical in his opposition to the boycott, questioning its motives. "It's not foreign policy, it's to fool the American people again -- to win the election," he said.

"Is Carter ashamed of our anthem? All the people want to hear the national anthem of the United States. America wants to be, and should be, the leader of the free world. People ought to hear the anthem."

Patterson arrived in the Soviet Union July 5, and toured Siberia and Uzbekistan before arriving in Moscow on Friday, the eve of the Olympics. He had no trouble getting his flag through customs.

"one officer asked a question, and another guy waved him off," he recalled. He said 'Let it go through, no problem at all.'"

Patterson said he had no pressure from government officials in the U.S. to cancel his trip, to no problem getting a visa and only scattered criticism from acquaintances.

"I got a little static from another American tourist here who said I represented a small majority of the American public. I couldn't understand why he came if he felt that way.

"A friend of mine at home said he was against contributing American dollars to the Soviet economy by coming here, but I think you should separate the people from the government.

"The people are what makes a country. If the people can get along -- especially the youth, through sports -- that's just marvelous . . . the Olympics prompted my trip, but meeting Soviet people is what I've enjoyed most. When you meet them one to one, on a personal basis, they're very congenial. They'll do anything they can for you. Their whole heart goes out to you."

No ugly American, Patterson did his best to learn some Russian before this trip, through a tape cassette course. "It helps a lot, communicating with the people," he said. "What you don't learn, you can make up with sign language and phrase books. But the people appreciate your making the effort to try to speak their language.

"I talked to some friends who have been to the Soviet Union, and read a lot about it before I left. It's a curiosity and an adventure to come here, because it's kind of a closed part of the world. It's a privilege to travel here, and we have been treated very well."

Patterson and the rest of his group will attend the Games and tour Moscow until Friday, when they fly to Helsinki and then back to New York. They had their pick of tickets to Olympic events -- the opening ceremonies, track and field, gymnastics, swimming -- because the initial American allotment of 192,000 tickets was virtually untouched.

Patterson's only moment of flickering self-doubt came when a reporter asked if he was aware of the flag-raising controversy of the last few days, and the White House's letter to Olympic officials voicing "strong objection" to any use of the Stars and Stripes or the "Star-Spangled Banner" at the Moscow Games.

"No, I wasn't aware of that at all," he said, his face suddeningly taking on a quizzical look. He wiped his brow with the sleeve of his white wind-breaker when asked if knowing that would have given pause.

"President Carter asked for it not to be done? Gosh," he said after a long pause. "I don't know, I just don't know."

The flag was folded neatly on his lap. It stayed there the rest of the afternoon. But Nick Paul, sensing that his young friend was puzzled and troubled, patted him on the back reassuringly. He was confident they had done the right thing.

To the old man in the greek cap who had worked the kitchens of all the good New York hotels, the flag means the freedom to act according to your conscience and convictions whatever the setting and the circumstances. He was proud of Patterson, and proud to have helped wave the flag today in Lenin Central Stadium.