Using the OR function with an array constant

I want to be able to determine if a certain chosen date, in some cell, is among the serial numbers included within an array constant).
For example, ={41640,41659,41687,41749,41785,41824,41883,41925,41954,41970,41971,41998} are the serial numbers of holidays for 2014.
If there is a date serial number in cell A4, I want to be able to have it compared to all the numbers, in the array. If it exists, in the array, I want to be informed.
I have been trying to do this using the OR function, but I have been unsuccessful at creating the formula which works. Additionally, I will be combining the result of this first step, with the IF function, to perform another step. I will appreciate any thoughts towards this goal.

Thank you very much, I will have great use for this.

Thank you so much, I am now using this. Even though I did not ask, but I discovered this array constant cannot be used in a formula (which equates to TRUE) in the conditional format feature. I had to write it differently to get it to work. =OR(A1=41640,A1=41659,etc). I am using the array constant within an IF function, to test for holidays, it works like a charm.