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%I
%S 0,1,2,3,4,5,6,7,8,9,7,8,9,10,11,12,13,14,15,16,14,15,16,17,18,19,20,
%T 21,22,23,21,22,23,24,25,26,27,28,29,30,28,29,30,31,32,33,34,35,36,37,
%U 35,36,37,38,39,40,41,42,43,44,42,43,44,45,46,47,48,49,50,51,49,50,51,52
%N Map n = Sum c_i 10^i to a(n) = Sum c_i 7^i.
%K nonn,base
%O 0,3
%A _N. J. A. Sloane_.
%E More terms from _Erich Friedman_.