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On the septimic character of 2 and 3

Published online by Cambridge University Press:  24 October 2008

Helen Popova Alderson
Affiliation:
Department of Pure Mathematics, Cambridge

Extract

Let e be an integer greater than 1 and let pbe a prime such that p ≡ 1 (mod e). Criteria for 2 to be a residue of degree e modulo p have been obtained in various forms for e = 2, 3, 4 and 5. Thus, Euler and Lagrange proved that 2 is a quadratic residue mod p if and only if p ≡ ± 1 (mod 8). Gauss showed that 2 is a cubic residue mod p if and only if p is representable as p = l2 + 27m2 with integers l and m, and that 2 is a quartic residue mod p if and only if p is representable as p = 12 + 64m2. Lehmer (5) and Alderson (1) have found similar but more complicated conditions for 2 to be a quintic residue mod p. There are analogous results about 3. For example, it follows from quadratic reciprocity that 3 is a quadratic residue mod p if and only if p ≡ ± 1 (mod 12), and Jacobi(4) showed that 3 is a cubic residue mod p if and only if 4p is representable as l2 + 35m2.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1973

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References

REFERENCES

(1)Alderson, H.On the quintic character of 2. Mathematika 11 (1964), 125130.Google Scholar
(2)Dickson, L. E.Cyclotomy, higher congruences and Waring's problem. Amer. J. Math. 57 (1935), 391424.Google Scholar
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