Unregistered users don't show up on the user list (see this meta.SE request) unless you type in their exact display name, but moderators have a way to search for users based on OpenID, email, or display name, which does search unregistered users.
]]>I have merged these two accounts.
]]>http://mathoverflow.net/users/3201/gerhard-paseman http://mathoverflow.net/users/3206/gerhard-paseman
]]>I can't find any of "Gerhard Paseman"'s accounts. Could you tell me the user numbers?
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