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p025.py
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p025.py
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# 1000-digit Fibonacci number
# Problem 25
# The Fibonacci sequence is defined by the recurrence relation:
# Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1.
# Hence the first 12 terms will be:
# F1 = 1
# F2 = 1
# F3 = 2
# F4 = 3
# F5 = 5
# F6 = 8
# F7 = 13
# F8 = 21
# F9 = 34
# F10 = 55
# F11 = 89
# F12 = 144
# The 12th term, F12, is the first term to contain three digits.
# What is the index of the first term in the Fibonacci sequence to contain 1000 digits?
def compute():
return fibonacci(1000)
def fibonacci(length):
fib =[1,1]
i = 1
while len(str(fib[i])) < length:
i = i + 1
fib.append(fib[i-1] + fib[i-2])
return (i + 1)
if __name__ == "__main__":
print(compute())