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%I #10 Sep 21 2021 15:47:28
%S 1,-15,-5,-17,-19,-21,1,-3,1,1,5,3,-33,1,-35,-5,5,-39,-13,-41,3,1,1,
%T -15,-3,3,5,15,-7,-51,1,3,-55,1,-5,5,-3,1,-21,-65,5,13,-69,3,-15,5,
%U -11,7,3,-17,17,-89,29,-91,13,-95,-5,33,1,-15,35,39,11,5,1,3,19,5,-11,5,-51,5,53,-165,-7,-3,1,21,-29,-5,21
%N Consider real quadratic fields of ERD-type with class groups of exponent 2 and discriminants of the form D = r^2*k^2+4k, k odd; sequence gives values of k.
%C Excludes discriminants appearing in A051990.
%D R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A4(3), column k.
%Y Cf. A051990, A051991, A051992, A051993, A051994, A051995, A051996, A051997.
%K sign,fini,full
%O 1,2
%A _N. J. A. Sloane_, Jan 04 2000
%E a(69) and following from _Georg Fischer_, Sep 21 2021