Minimum 1's to get 1-expression for n
Wolfram Language (Mathematica), 76 71 bytes

If[#&lt;2,1,Min[#+Reverse@#&amp;/@{#0/@Range[#-1],#0/@Most@Rest@Divisors@#}]]&amp;


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The recursive approach: define f[n] to be the minimum of f[k]+f[n-k]over all k less than n, and f[d] + f[n/d]over all divisors of n (other than 1 and n itself).