Using Python

Consider the following sequence of numbers 1, 1, 1, 3, 5, 9, 17, 31, 57. the first 3 numbers are 11 and 1. Every subsequent number is the sum of the previous 3 numbers. This the 4th number is the sum of 1, 1, 1 = 3. The fifth number is the sum of. 1, 1, 3 thus 5. The sixth number is the sum of 1, 3, 5 thus 9 and so on and so forth. given n output the nth number in this sequence. sample output: enter n: 6 the answer is. 9