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%I #13 Sep 21 2021 14:44:56
%S 1,-1,1,5,-1,3,-7,1,-3,-5,5,-11,1,-1,1,13,-1,7,-15,-3,5,-1,1,3,1,-5,
%T 21,-1,1,1,-13,-15,3,15,-31,1,-1,1,17,-35,-7,5,-1,1,19,-39,-3,-5,5,41,
%U 3,5,-23,1,1,-3,17,13,-1,-19,-29,1,-3,5,-31,21,33,-3,-7,35,3,1,-15,-19,-39,5,41,-21,-11,11,5,1,5,-55,55,29,5,-11,1,-35,35,1,-7,-3,1,1,-15,21
%N Consider real quadratic fields of ERD-type with class groups of exponent 2 and discriminants of the form D = r^2*k^2+k, k odd; sequence gives values of k.
%D R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A4(1), column k.
%Y Cf. A051990, A051991, A051992, A051993, A051994, A051995, A051997, A051998.
%K sign,fini,full
%O 1,4
%A _N. J. A. Sloane_, Jan 04 2000
%E a(73) and following from _Georg Fischer_, Sep 21 2021