%I #33 Oct 16 2023 23:48:45
%S 1,1,1,1,1,1,1,1,1,6,7,4,4,4,3,5,5,4,3,5,6,6,4,3,2,4,4,4,4,3,4,3,4,4,
%T 4,2,4,4,4,5,5,5,4,5,3,4,5,3,4,3,4,4,4,4,4,4,4,4,4,5,5,3,4,3,4,4,5,5,
%U 4,5,5,5,4,4,4,6,6,4,4,4,4,4,5,5,4,5,5,5,3,3,4,4,4,4,4,4,4,4,4,8,9
%N Minimum number of digits required to represent n only using digits present in n.
%C The only operations allowed are addition, subtraction, multiplication, division, exponentiation, and parenthesizing. Concatenation is not allowed.
%H Valentin Miakinen, <a href="https://github.com/RedStorm1024/MPDR-Bruteforcer/blob/main/btdmathchallenge.py">Python program</a>
%e For n = 10, a solution for a(10)=6 is (1+1+1)^(1+1)+1.
%e For n = 27, a solution for a(27)=4 is 2+(2-7)^2.
%o (Python) # See Miakinen link.
%Y Cf. A043537.
%K nonn,base
%O 1,10
%A _Oskar Macholl_, Valentin Miakinen, and _Walter Robinson_, May 02 2023
%E Edited by _N. J. A. Sloane_, Oct 16 2023.