43 lines
702 B
Python
43 lines
702 B
Python
#!/usr/bin/env python3
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from math import ceil
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def reducetwo(n):
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c = 0
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while not n%2:
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n //= 2
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c += 1
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return n, c
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def primes(n):
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sieve = [0] * (n//2)
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for p in range(3, n, 2):
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if sieve[p//2] > 0:
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continue
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for k in range(1, n//p+1, 2):
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sieve[(p*k)//2] += p + sieve[k//2] - sieve[(p*k)//2]
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return sieve
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n = 2*10**7
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k = 15*10**6
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sieve = primes(n)
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print("Primed.")
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s = 0
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for m in range(n, n-k, -1):
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if not m % 2:
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m, c = reducetwo(m)
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s += 2*c
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s += sieve[m//2]
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print("Calculated.")
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for m in range(2, k+1):
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if not m % 2:
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m, c = reducetwo(m)
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s -= 2*c
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s -= sieve[m//2]
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print(s)
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