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A366602
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Number of divisors of 4^n-1.
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11
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2, 4, 6, 8, 8, 24, 8, 16, 32, 48, 16, 96, 8, 64, 96, 32, 8, 512, 8, 192, 144, 128, 16, 768, 128, 128, 160, 256, 64, 4608, 8, 128, 384, 128, 512, 8192, 32, 128, 192, 768, 32, 9216, 32, 1024, 4096, 512, 64, 6144, 32, 8192, 1536, 1024, 64, 10240, 3072, 2048, 384
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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)=8 because 4^4-1 has divisors {1, 3, 5, 15, 17, 51, 85, 255}.
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MAPLE
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a:=n->numtheory[tau](4^n-1):
seq(a(n), n=1..100);
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MATHEMATICA
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DivisorSigma[0, 4^Range[100]-1] (* Paolo Xausa, Oct 14 2023 *)
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PROG
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(PARI) a(n) = numdiv(4^n-1);
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CROSSREFS
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Cf. A046798, A046801, A366575, A366612, A366621, A366633, A366652, A366661, A070528, A366683, A366709.
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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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