39 lines
779 B
Python
39 lines
779 B
Python
#!/usr/bin/env python3
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def getprimes(n):
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sieve = [True] * n
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for p in range(3, n, 2):
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if not sieve[p]:
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continue
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for i in range(p**2, n, 2*p):
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sieve[i] = False
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return sieve
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def is_prime(n):
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if n == 2:
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return True
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return n % 2 and sieve[n]
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N = 10**8
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sieve = getprimes(N)
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primes = [2] + [n for n in range(3, N, 2) if sieve[n]]
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for n in range(2, int(N**0.5)+1):
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b = n**2
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if n % 2:
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b *= 2
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for i in range(b, N, b):
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sieve[i] = n
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s = 0
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for p in primes:
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d = sieve[p+1]
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k = d + 1
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while ((p+1) * k**2)/d**2 <= N:
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if is_prime(((p+1)*k)//d - 1) and is_prime(((p+1)*k**2)//d**2 - 1):
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s += p + ((p+1)*k)//d - 1 + ((p+1)*k**2)//d**2 - 1
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k += 1
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print(s)
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