public static Set<List<Integer>> getRollUpPermutationsAsPositions(final int tagCount) {
        final Set<List<Boolean>> resultSet = getRollUpPermutationsAsBooleans(tagCount);

        final Set<List<Integer>> perms = new HashSet<>();

        for (final List<Boolean> perm : resultSet) {
            perms.add(new ArrayList<>(buildPositionList(perm)));
        }

        return perms;
    }
@param tagCount The number of tags you want permutations for
@return A set of rolled up tag positions for the passed number of tags,
e.g. 2 => [ [], [0], [1], [0,1] ]
stroom-statistics/stroom-statistics-impl-hbase/src/main/java/stroom/statistics/impl/hbase/rollup/RollUpBitMask.java