James Wanless on Wed, 22 Oct 2008 21:00:59 +0200

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Lists of class numbers of imaginary quadratic fields - help pls?

1) Thanks to the devs for PARI/GP, I have already found it very useful and fun, and if it can solve my problem here I'll be very grateful!
2) I'm trying to use/modify the following program (from OEIS) to generate above lists (up to h=50 or even above, hopefully):
{ bnd = 10000; S = vector(10, X, []); for (i = 1, bnd, if (issquarefree(i), n = qfbclassno(if(i%4==3, -i, -4*i)); if (n<11, S[n] = concat(S[n], i), ), )); }
3) I'm using gp V2.3 on a PPC iMac G5 (in case that's relevant)
4) When I compare lists for the first few h, there is a good, but not perfect match with the tables at http://mathworld.wolfram.com/ClassNumber.html
Why is that, please? And which should I trust? [or are they both right and there is some mapping involving genera I need to consider?]
James (Wanless)