26 lines
400 B
Python
26 lines
400 B
Python
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#!/usr/bin/env python3
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def primes(n):
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sieve = [False] * n
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for p in range(2, n):
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if sieve[p]:
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continue
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for i in range(p**2, n, p):
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sieve[i] = True
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return sieve
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bound = 10**6
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sieve = primes(bound)
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c = 0
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n = 1
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cube_diff = 7
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while cube_diff < bound:
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if not sieve[cube_diff]:
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c += 1
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n += 1
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cube_diff = 3*n**2 + 3*n + 1
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print(c)
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