Do you mean that you sum over all indices except the first and last? i there looks like it runs from 1 to 10, not 100. (But something else could label which indices don’t get summed, the nth & mth.) You could write this, but there’s little to gain over writing the loops yourself:
julia> inds = rand(1:10, 333, 100); vals = randn(333);
julia> out = zeros(10,10);
julia> using Tullio
julia> @tullio out[inds[r,1], inds[r,100]] += vals[r]