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Prime-valued polynomials

Published online by Cambridge University Press:  01 August 2016

K. Robin McLean*
Affiliation:
Department of Education, University of Liverpool, P.O. Box 147, Liverpool L69 3BX

Extract

In a recent Note Nick Lord proved that if a polynomial f(x) of degree n takes prime values for 2n + 1 integer values of x, then it is irreducible. (All polynomials discussed here are assumed to have integer coefficients and, like Lord, I regard numbers of the form –p where p is a positive prime as primes in their own right.) He wondered whether his result is the best possible one of its kind. If we restrict attention to positive primes, a best possible result can be achieved (Theorems 2 and 3 below). When we allow negative primes, Lord's result can be improved (see Theorems 1, 3 and 4) by an observation which still surprises me.

Type
Articles
Copyright
Copyright © The Mathematical Association 1998

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References

1. Lord, N. Prime values of polynomials, Math. Gaz. 79 (November 1995) pp. 572573.CrossRefGoogle Scholar
2. Hardy, G. H. and Littlewood, J. E. Some problems of partido numerorum: III On the expression of a number as a sum of primes, Acta Mathematica 44 (1923) pp. 170.Google Scholar
3. Boston, N. and Greenwood, M. L. Quadratics representing primes, American Mathematical Monthly 102 (August-September 1995) pp. 595599.Google Scholar
4. Schinzel, A. and Sierpinski, W. Sur certaines hypothèses concernant les nombres premiers, Acta Arithmetica 4 (1958) pp. 185208.Google Scholar