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A117582 For successive primes p, the number of ratios of the form n^2/(n^2-1) which factor into primes less than or equal to p. 2

%I

%S 0,2,5,10,15,24,34,46,57,74,90,114,141

%N For successive primes p, the number of ratios of the form n^2/(n^2-1) which factor into primes less than or equal to p.

%C By a theorem of Størmer, the number of ratios m/(m-1) factoring into primes only up to p is finite. A proportion of these have square denominators.

%H E. F. Ecklund and R. B. Eggleton, <a href="http://www.jstor.org/stable/2317422">Prime factors of consecutive integers</a>, Amer. Math. Monthly, 79 (1972), 1082-1089.

%H D. H. Lehmer, <a href="http://projecteuclid.org/euclid.ijm/1256067456">On a problem of Størmer</a>, Ill. J. Math., 8 (1964), 57-79.

%Y Cf. A002071, A117583.

%K hard,nonn

%O 0,2

%A _Gene Ward Smith_, Apr 02 2006

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)