%I M0225 #24 Jan 27 2018 06:30:56
%S 1,1,2,2,2,2,4,4,4,2,6,6,4,4,4,2,6,8,4,4,6,4,2,6,8,8,8,8,4,4,10,8,4,4,
%T 4,10,12,4,8,4,14,4,8,6,6,12,8,8,6,10,12,4,4,14,8,8,8,4,8,16,14,8,6,8,
%U 16,8,10,12,14,12,4,8,10,12,16,12,4,4,20,10,12,6,8,20,20,8,8,6,8,10,16
%N Class number of quadratic field with discriminant -4n as n runs through A089269: squarefree numbers congruent to 1 or 2 mod 4.
%C Equivalently, number of classes of primitive positive definite binary quadratic forms of discriminant -4n as n runs through A089269: squarefree numbers congruent to 1 or 2 mod 4.
%D D. A. Buell, Binary Quadratic Forms. Springer-Verlag, NY, 1989, pp. 224-241.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H N. J. A. Sloane, <a href="/A006643/b006643.txt">Table of n, a(n) for n = 1..10000</a>
%o (PARI) for (n=1,50, if(issquarefree(n) && (n%4 == 1 || n%4 == 2), print(n, " ", qfbclassno(-4*n)))) \\ _N. J. A. Sloane_, May 28 2014
%Y Cf. A006642, A089269, A014599.
%Y A subsequence of A000003.
%K nonn
%O 1,3
%A _N. J. A. Sloane_, _Mira Bernstein_
%E Extended and definition corrected by _Max Alekseyev_, Apr 16 2010