22 lines
334 B
Python
22 lines
334 B
Python
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#!/usr/bin/env python3
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def pell3():
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x, y = 2, 1
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while True:
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yield x, y
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x, y = 2*x + 3*y, 2*y + x
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max_perimiter = 10**9
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s = 0
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for x, y in pell3():
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p = 12*(2*y**2 + x*y) + 2
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if p <= max_perimiter:
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s += p
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p = 6*(x**2 - y**2) - 2
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if p > max_perimiter:
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break
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s += p
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print(s)
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