BuSalem Numbers starts with 1 1 1 (first, second and third BuSalem numbers respectively) then every other number is the summation of the last three numbers, hence the fourth BuSalem number is 1+1+1 = 3, the Fifth Busalem number is 1+1+3=5, the sixth BuSalem number is 1+3+5=9 and so on.
write a program to find the nth BuSalem number. You must use functions.