33 lines
677 B
Python
33 lines
677 B
Python
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from math import gcd
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from lib_prime import is_prime_rabin_miller
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def r_modulo_closed_form(n, m):
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assert n > 0 and m > 0
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return ((pow(10, n, 9 * m) - 1) // 9) % m
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def a_special(n):
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k = n - 1
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if r_modulo_closed_form(k, n) == 0:
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return k
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return None
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def euler_130():
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c, r = 0, 0
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for n in range(2, 10**9):
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if gcd(n, 10) == 1 and not is_prime_rabin_miller(n):
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if a_special(n) is not None:
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r += n
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c += 1
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if c == 25:
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break
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return r
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if __name__ == "__main__":
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solution = euler_130()
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print("e130.py: " + str(solution))
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assert(solution == 149253)
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