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A120357
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a(n) is the smallest prime p such that 2^p-1 (a Mersenne number) contains 10^n or more decimal digits.
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1
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2, 31, 331, 3319, 33223, 332191, 3321937, 33219281, 332192831, 3321928097, 33219280951, 332192809589, 3321928094941, 33219280948907, 332192809488739, 3321928094887411, 33219280948873687, 332192809488736253
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OFFSET
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0,1
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COMMENTS
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For n>0 almost all digits of a(n) from the left are equal to the first terms of the expansion Log[10]/Log[2] = {3, 3, 2, 1, 9, 2, 8, 0, 9, 4, 8, 8, 7, 3, 6, 2, 3, 4, 7, 8, 7, 0, 3, 1, 9, 4, 2, 9, 4, 8, 9, 3, 9, ...} = A020862(n). - Alexander Adamchuk, Jan 16 2007
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LINKS
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Author?, GIMPS [Broken link?]
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EXAMPLE
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E.g. a(7)=33219281 because 2^33219281-1 is the smallest Mersenne number that contains 10^7 (ten million) or more decimal digits.
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CROSSREFS
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Cf. A020862 = decimal expansion of log(10)/log(2).
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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