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a(n) is the least k > 0 such that k and 3k are anagrams in base n (written in base 10).
1

%I #12 Mar 20 2017 23:13:07

%S 75,142,315,12,819,84,1035,15,198,2766,9555,56,315,8352,20893,45,950,

%T 22000,819,132,63204,24492,114075,91,2646,938,30015,240,182807,118592,

%U 333795,153,5670,187416,73815,380,623610,176820,5699,231,10406,489808

%N a(n) is the least k > 0 such that k and 3k are anagrams in base n (written in base 10).

%C 2*a(n) is divisible by n-1. - _Robert Israel_, Mar 20 2017

%p for n from 4 to 100 do

%p searching:= true:

%p if n::even then delta:= n-1 else delta:= (n-1)/2 fi;

%p for d from 1 while searching do

%p for x from n^(d-1)+delta-1 to floor(n^d/3) by delta while searching do

%p if sort(convert(x,base,n)) = sort(convert(3*x,base,n)) then

%p searching:= false; A[n]:= x;

%p fi

%p od od od:

%p seq(A[i],i=4..100); # _Robert Israel_, Mar 20 2017

%t Table[k = 1; While[! Equal @@ Map[Sort@ IntegerDigits[#, n] &, {k, 3 k}], k++]; k, {n, 4, 45}] (* _Michael De Vlieger_, Mar 20 2017 *)

%K nonn,base

%O 4,1

%A _David W. Wilson_