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%I #9 Dec 14 2019 21:33:40
%S 1,1,1,2,2,1,2,1,2,3,2,3,1,4,2,2,4,4,4,2,4,3,2,2,4,3,5,4,1,3,3,2,4,3,
%T 4,2,2,4,5,6,6,1,6,4,4,3,6,6,4,3,3,2,4,6,4,7,2,4,5,5,3
%N a(n) is the number of orbits under the action of GL_2[Z] on the primitive binary quadratic forms of discriminant D, where D=m if m=1 (mod 4), D=4*m otherwise and m<0 is the n-th squarefree number.
%C A000924 is the same except it is under the action of SL_2[Z].
%H S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/">Class number theory</a>
%H Steven R. Finch, <a href="/A000924/a000924.pdf">Class number theory</a> [Cached copy, with permission of the author]
%H Jens Jonasson, <a href="http://www.mai.liu.se/~jejon/">Classes of integral binary quadratic forms</a>, Master's thesis (2001), Appendix B.
%e m = -1, -2, -3, -5, -6, -7, -10, -11, -13, ...
%e with corresponding discriminant
%e D = -4, -8, -3, -20, -24, -7, -40, -11, -52, ....
%Y Cf. A000924.
%K nonn
%O 1,4
%A _Steven Finch_, May 05 2005
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