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Minimum number of digits required to represent n only using digits present in n.
2

%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.