What is the sequence pattern in 1 I 2 l 3 F 4?

The sequence alternates between numbers and letters. The numbers increase sequentially (1, 2, 3, 4), while the letters appear to be specific characters: "I," "l," and "F," which represent the first letter of the respective sequence (where "l" is the lowercase letter "L"). The pattern suggests a combination of numeric progression with selective letters. The next expected element would likely be "5" followed by another letter.