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A366576
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Sum of the divisors of 3^n-1.
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9
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3, 15, 42, 186, 399, 1680, 3282, 15876, 31836, 123690, 277344, 1541568, 2391486, 8992680, 25483332, 111757968, 193819392, 967814400, 1744488660, 9366647892, 16912999320, 62424587520, 144219337920, 852903426816, 1397135488896, 4766016364260, 12477973754400
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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(4)=186 because 3^4-1 has divisors {1, 2, 4, 5, 8, 10, 16, 20, 40, 80}.
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MAPLE
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a:=n->numtheory[sigma](3^n-1):
seq(a(n), n=1..100);
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MATHEMATICA
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DivisorSigma[1, 3^Range[30]-1] (* Paolo Xausa, Oct 15 2023 *)
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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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