function pcombos(str)

# `S` is indexed by characters, where each element
# is a list of indices the character appears within `str`
S = Dict{Char,Array{Int64,1}}()
#combos = fill([1 1 1 1], (0))
total = 0

for (i, ch) in enumerate(str)
    push!(get!(S, ch, fill(0, (0))), i)
end
for a in 1:length(str)-3
    for d in reverse(S[str[a]])
        d <= a && break
        for b in a+1:d-1
            for c in reverse(S[str[b]])
                c >= d && continue
                c <= b && break
                #println([a b c d])
                #push!(combos, [a b c d])
                total += 1
            end
        end
    end
end

#return length(combos)
return total

end #function