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A062173
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a(n) = 2^(n-1) mod n.
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27
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0, 0, 1, 0, 1, 2, 1, 0, 4, 2, 1, 8, 1, 2, 4, 0, 1, 14, 1, 8, 4, 2, 1, 8, 16, 2, 13, 8, 1, 2, 1, 0, 4, 2, 9, 32, 1, 2, 4, 8, 1, 32, 1, 8, 31, 2, 1, 32, 15, 12, 4, 8, 1, 14, 49, 16, 4, 2, 1, 8, 1, 2, 4, 0, 16, 32, 1, 8, 4, 22, 1, 32, 1, 2, 34, 8, 9, 32, 1, 48, 40, 2, 1, 32, 16, 2, 4, 40, 1, 32, 64, 8, 4, 2, 54, 32, 1, 58, 58, 88, 1, 32, 1, 24, 46
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OFFSET
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1,6
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COMMENTS
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If p is an odd prime then a(p)=1. However, a(n) is also 1 for pseudoprimes to base 2 such as 341.
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LINKS
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FORMULA
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EXAMPLE
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a(5) = 2^(5-1) mod 5 = 16 mod 5 = 1.
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MATHEMATICA
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PROG
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(Haskell)
import Math.NumberTheory.Moduli (powerMod)
(Magma) [Modexp(2, n-1, n): n in [1..110]]; // G. C. Greubel, Jan 11 2023
(SageMath) [power_mod(2, n-1, n) for n in range(1, 110)] # G. C. Greubel, Jan 11 2023
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CROSSREFS
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Cf. A176997 (after the initial term, gives the positions of ones).
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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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