=encoding utf8

=head1 NAME

pds_48.db - larger database with planar difference set samples

=head1 VERSION

This is version 0.9 of the database, created on September 17, 2019.

=head1 DESCRIPTION

This file is a slightly larger sample database only used for testing.

It contains 48 cyclic planar difference sets with orders ranging from
2 to 149.  The sets are generated from Conway polynomials.

=head1 FILE FORMAT

SQLite 3.x database.

=head1 SCHEMA

  CREATE TABLE difference_set (
    order_   integer NOT NULL PRIMARY KEY,
    base     integer NOT NULL,
    exponent integer NOT NULL,
    modulus  integer NOT NULL,
    n_planes integer NOT NULL,
    deltas   text    NOT NULL
  );

=head1 DATA REPRESENTATION

If I<D = { d_1, d_2, ..., d_k } (mod m)> is a canonical cyclic planar
difference set of order I<k - 1> with I<d_1 E<8801> 0> and
I<d_1 E<8801> 1 (mod m)>, I<deltas> is a string with I<k - 2> numeric
values separated by blanks, calculated as differences of consecutive
residue values of I<D> starting with I<d_3 - d_2>.  The difference of
the smallest two values in a canonical set is always 1 and thus not
important to store.

=head1 PROVIDER

Martin Becker, E<lt>becker-cpan-mp I<at> cozap.comE<gt>

=head1 COPYRIGHT AND LICENSE

The contents of this database are mathematically defined entities.
The provider believes mathematical constants not to be proprietary or
subject to copyright legislation, although the software used to calculate
them may be.

=cut
