20. Patrick asks SpongeBob: "What is your lucky number?" SpongeBob says: "There is a sequence of numbers: $0,1,3,8$, $21,55,144,377,987, \cdots \cdots$ Starting from the third number, each number multiplied by 3 is exactly equal to the sum of the numbers immediately before and after it. My lucky number is the remainder when the 2020th number in this sequence is divided by 6." So, SpongeBob's lucky number is $\qquad$ . (If it is divisible, then the remainder is 0)
$2$