President Trump earlier this year purchased more than $1 million in the stock of Dell Technologies, a transaction that is drawing scrutiny after the Pentagon this week announced a $9.7 billion contract with the Texas-based computer company.

The sequence of events illustrates the complications that emerge when a sitting president continues, even if through financial advisers, to buy and sell publicly traded stocks like Dell.

In the first three months of this year, Mr. Trump’s investment portfolio executed more than 3,600 trades, a mandatory disclosure form shows, buying and selling shares in big banks, manufacturers and tech giants, among other companies.

The document shows a Dell stock purchase of $1 million to $5 million in February, and smaller amounts in the months since. (The document includes ranges in some cases, rather than specific amounts.)

The Trump family has argued that the president does not personally control the trading, saying these are automated trades placed by outside brokerage firms.

“This structure was intentionally designed to maintain a clear separation between President Trump and the independent third-party investment managers overseeing the accounts and avoid even the appearance of any conflict of interest,” the Trump Organization said in a statement earlier this month.