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Least number x such that x^n has n digits equal to k. Case k = 9.
2

%I #9 May 05 2017 18:23:48

%S 9,63,99,131,99,983,864,1091,2137,1349,2053,3686,4053,5741,9609,3822,

%T 11924,7533,9096,22387,13502,5912,26942,19603,41735,46946,32113,56205,

%U 74549,99624,58129,83731,93528,74023,92956,67972,124262,119865,30499,81629,61259,143197

%N Least number x such that x^n has n digits equal to k. Case k = 9.

%e a(4) = 131 because 131^4 = 294499921 has 4 digits '9' and is the least number to have this property.

%p P:=proc(q,h) local a,j,k,n,t; for n from 1 to q do for k from 1 to q do

%p a:=convert(k^n,base,10); t:=0; for j from 1 to nops(a) do if a[j]=h then t:=t+1; fi; od;

%p if t=n then print(k); break; fi; od; od; end: P(10^9,9);

%K nonn,base,easy

%O 1,1

%A _Paolo P. Lava_, Apr 19 2017