19. In a "TriboNcci" sequence, each number after the third number is the sum of the preceding three numbers. For example, if the
first three numbers are 5,6, and 7 , then the fourth number is 18 because 5 + 6 + 7 = 18, and the fifth number is 31 because 6 + 7 + 18 = 31. The first five numbers of another TriboNcci sequence are P, Q, 86, 158, and 291 in that order. What is the value of P ?
Answer: each number after the third number is the sum of the preceding three numbers. For example, if the first three numbers are 5, 6, and 7, then the fourth number is 18 because 5 + 6 + 7 = 18 and the fifth number is 31 because 6 + 7 + 18 = 31.
