The Student Loan Marketing Association yesterday reported net income of $99.3 million ($1.91 per share) in 1984, up 49 percent over profits of $66.6 million ($1.37) the year before.

Sallie Mae, as the federally chartered association is known, reported fourth-quarter earnings of $27.1 million (53 cents), up 31 percent from $20.7 million (39 cents).

The association is the nation's major financier of federally sponsored student loan programs, buying federally insured student loans and making loans to private lenders so they can make loans to students.

Loans purchased or advanced by Sallie Mae totaled $2.7 billion last year, a 13 percent increase over 1983. The corporation's loan portfolio was $5.6 billion at year end, 22 percent higher than a year before.

Entre' Computer Centers Inc., a franchiser of retail computer stores, reported profits of $2.5 million (26 cents) on revenue of $7.9 million in its fiscal first quarter ended Nov. 30. The results reflected a 150 percent increase from earnings of $1 million (13 cents) on revenue of $3.7 million the previous year.

The Vienna company opened 30 new franchised centers during the quarter, bringing the total number to 233, with an additional 49 centers under development.

Retail sales of computers and related equipment and software through the Entre' network rebounded strongly in October and November after being hurt by the unavailability of certain product lines in September, the company said.