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A366661
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Number of divisors of 9^n-1.
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12
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4, 10, 16, 24, 24, 80, 16, 112, 128, 180, 64, 384, 16, 160, 768, 256, 128, 1280, 64, 864, 768, 640, 32, 14336, 384, 160, 4096, 1536, 256, 23040, 128, 576, 2048, 1280, 768, 12288, 128, 640, 12288, 16128, 128, 61440, 32, 12288, 196608, 320, 512, 131072, 2048
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(2)=10 because 9^2-1 has divisors {1, 2, 4, 5, 8, 10, 16, 20, 40, 80}.
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MAPLE
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a:=n->numtheory[tau](9^n-1):
seq(a(n), n=1..100);
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MATHEMATICA
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DivisorSigma[0, 9^Range[100]-1]
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PROG
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(PARI) a(n) = numdiv(9^n-1);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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