<cfset aDoors = arrayNew(1)/>
<cfloop from=1 to=100 index="i">
    <cfloop from=1 to=100 index="y">
        <cfif arraylen(aDoors) LT y OR !len(aDoors[y])>
            <cfset aDoors[y] = 'closed'/>
        </cfif>
        <cfif y mod i eq 0>
            <cfif aDoors[y] eq 'closed'>
                <cfset aDoors[y] = 'open'/>
                <cfelse>
                <cfset aDoors[y] = 'closed'/>
            </cfif>
        </cfif>
    </cfloop>
</cfloop>

<cfdump var="#aDoors#"/>