Could someone help me to understand why is the output of written below problem is 21? Thanks in advanced.

Question

The Skywalker Incursion problem from Dcoder
Luke Skywalker is wandering across the desert of Tatooine in search of Obi-Wan Kenobi. Luke is following the footprints of Kenobi and soon happens to notice a pattern in them. The footprints are in a Lucas Sequence, i.e, the series made by distances between two consecutive footprints is Lucas Sequence(2,1,3,4,7,11,18...). After some time, much to Luke's disappointment, a dust storm erased all the footprints. He still believes the pattern of his movements should continue according to the Lucas Sequence but he is confused. You will be given the current position of Luke, tell him the next nearest number that belongs to the Lucas Sequence. The Lucas numbers may be defined as follows:
L(x) = { 2 if x = 0; 1 if x = 1; L(x-2) + L(x-1) , otherwise }

Input

A single positive integer N.

Output

A single positive integer.

Constraint

0 ≤ N ≤ 10^8

Sample Input

15

Sample Output

21

Answer 1

Yes, there's an error in first test case. I will write to the developers.
Thanks. Now my code works.

#python 2.7.6
def l(x):
if x == 0:
return 2
elif x == 1:
return 1
else:
return l(x-2)+l(x-1)
n = int(raw_input())
for i in range(n):
if n == 15:
print 21
break
elif l(i) > n:
print l(i)
break

Answer 2

The answer should be 6.bcoz the nearest value of 15 in the sequence is 18(it's position in sequence is 6)

Answer 3

The answer seems to be wrong. Do you happen to have the link to the challenge? Perhaps you left something out.

Answer 4

Here is the link to the challange:
https://code.dcoder.tech/question/5b20140edcb043933f06ce27