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COMMENTS
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The term "n-fold" refers to a covering set with n primes. For 271129, the covering set is {3, 5, 7, 13, 17, 241}. So we have a covering set with six primes (6-fold).
a(10) > 2^31. Other known values: a(11) = 1143502909. [Arkadiusz Wesolowski, Apr 29 2012]
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EXAMPLE
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271129 has the covering set {3, 5, 7, 13, 17, 241}.
78557 has the covering set {3, 5, 7, 13, 19, 37, 73}.
1777613 has the covering set {3, 5, 7, 13, 17, 19, 109, 433}.
169073869 has the covering set {3, 5, 7, 11, 13, 41, 61, 151, 331}.
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