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%I #27 Jan 25 2014 16:39:17
%S -4,-3,-20,-7,-11,-52,-68,-19,-23,-116,-31,-148,-164,-43,-47,-212,-59,
%T -244,-67,-71,-292,-79,-83,-356,-388,-404,-103,-107,-436,-452,-127,
%U -131,-548,-139,-596,-151,-628,-163,-167,-692,-179,-724,-191,-772,-788,-199
%N Choose smallest m>0 such that the n-th rational prime p ramifies in the imaginary quadratic extension field K = Q(sqrt(-m)); a(n) = discriminant(K).
%C m=1 if p=2, otherwise m=p.
%D David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989, Cor. 5.17, p. 105.
%H Bruno Berselli, <a href="/A220861/b220861.txt">Table of n, a(n) for n = 1..1000</a>
%F Let p = prime(n). Then a(n) = -4 if p = 2, -p if p == 3 mod 4, -4p if p == 1 mod 4.
%Y Cf. A088192, A220862, A220863.
%K sign
%O 1,1
%A _N. J. A. Sloane_, Dec 26 2012