Keep in mind that regex features are dependant on the language being used.
With Java, you can do this:
[acegikmoqstz@#&](?:.*[acegikmoqstz@#&]){2}
But that's all, with java you can't refer to named subpattern.
With PHP you can do that:
(?(DEFINE)(?<a>[acegikmoqstz@#&]))\g<a>(?:.*\g<a>){2}