Data from extensive computations on class groups of quadratic imaginary fields is available below. It is organized by fundamental discriminant $-d$, and divided into four groups based on congruences:

• $d\equiv 3\pmod 8$
• $d\equiv 7\pmod 8$
• $d\equiv 4\pmod {16}$
• $d\equiv 8\pmod {16}$
For each congruence class above, there are 4096 files, indexed from $k=0$ to $k=4095$. The $k$th file contains data for $k\cdot 2^{28} \leq |d| \lt (k+1)\cdot 2^{28}$. The files are named accordingly, so the $k=12$ file for $d\equiv 7\pmod8$ is called `cl7mod8.12.gz`, the final extension because it has been compressed with `gzip`. The compressed files range in size from 50 to 200 megabytes.

After uncompressing with `gzip`, files have the following format:

• There is one line per field
• Discriminants for a given file are listed in order (in absolute value)
• If $-d_i$ is the $i$th discriminant for a file, line $i+1$ has the form  $a$ $b$ $c_1 c_2 \ldots c_t$
to signify that
• $d_{i+1} = d_i+m\cdot a$, ($m$ is the modulus for the file)
• $h(-d_{i+1}) = b$,
• invariant factors for the class group are $[c_1, c_2,\ldots, c_t]$.
In particular, $b=\prod_{j=1}^t c_j$.

### Getting files

 $d \equiv$ 3 (mod 8) 7 (mod 8) 4 (mod 16) 8 (mod 16) $k =$ integer from 0 to 4095