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A105267
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a(n) = the number of divisors of 33...31, with n 3s.
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2
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1, 2, 2, 2, 2, 2, 2, 2, 4, 4, 4, 8, 8, 16, 4, 4, 8, 2, 8, 24, 8, 4, 16, 8, 8, 4, 16, 8, 8, 6, 8, 16, 64, 4, 4, 8, 8, 16, 16, 2, 8, 8, 64, 64, 8, 4, 8, 32, 8, 2, 8, 8, 16, 64, 8, 8, 32, 8, 32, 2, 8, 64, 32, 16, 8, 32, 8, 8, 32, 16, 64, 64, 8, 64, 4, 4, 16, 2
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OFFSET
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0,2
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COMMENTS
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The first seven 33...31 numbers are prime, so those terms are 2. - Don Reble, Oct 26 2006
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LINKS
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FORMULA
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MATHEMATICA
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a[n_] := DivisorSigma[0, (10^(n + 1) - 7)/3]; Array[a, 30, 0] (* Amiram Eldar, May 13 2020 *)
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PROG
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(PARI) a(n) = numdiv((10^(n + 1) - 7)/3); \\ Michel Marcus, May 13 2020
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CROSSREFS
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KEYWORD
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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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