<?php
$POSTmin = 6;
$POSTmax = 30;
$query = "SELECT Name, GROUP_CONCAT(SeqNumber) SeqNumbers
FROM mytable
WHERE SeqNumber BETWEEN ? AND ?
GROUP BY Name;";
// get DB version using PDO
$stmt = $pdo->prepare($query);
$stmt->execute([$POSTmin, $POSTmax]);
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
print_r($rows);