Using Python, write a recursive function to calculate and return the Nn number of the sequence S which satisfies the following recurrence relation: the first three number of the sequence are 0,1,2, from the 4th number, each one is equal to the sum of its preceding three numbers; i.e., given position n4, the Nth sequence number is: S(n)=S(n1)+S(n2)+S(n3) E.g., the 4th number =0+1+2=3, the 5th number =1+2+3=6, the 6th number = 2+3+6=11, etc