The expression you provided, "F 28 =", appears incomplete. Could you clarify what "F" represents in this context?

Common interpretations include:

1. Fibonacci Sequence: If "F" represents the Fibonacci sequence, then $F(28)$ would refer to the 28th Fibonacci number.
2. Function: If "F" is a function, I would need more information about the function's definition to solve for $F(28)$.

Please provide more details so I can help you accurately.

Would you like to explore one of these interpretations? If so, I can provide the corresponding result or help with further calculations.