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%I A072998 #22 Mar 31 2021 04:54:48
%S A072998 1,2,20,21,22,200,201,202,210,211,212,220,221,222,2000,2001,2002,2010,
%T A072998 2011,2012,2020,2021,2022,2100,2101,2102,2110,2111,2112,2120,2121,
%U A072998 2122,2200,2201,2202,2210,2211,2212,2220,2221,2222,20000,20001,20002,20010
%N A072998 To get a(n), write n in balanced ternary notation (using only digits -1, 0, 1, -1), then change -1's to 0's, 0's to 1's, and 1's to 2's.
%e A072998 n balanced ternary a(n)
%e A072998 -----------------------
%e A072998 0........0...........1
%e A072998 1........1...........2
%e A072998 2......1,-1..........2,0
%e A072998 3.......1,0..........2,1
%e A072998 ...
%e A072998 11 in base 10 = 11_10 = {1,1,-1} in balanced ternary = 1*3^2 + 1*3^1 - 1*3^0. Add 111 to {1,1,-1} to get a(11) = 220.
%K A072998 base,nonn
%O A072998 0,2
%A A072998 _Robert G. Wilson v_, Aug 15 2002
%E A072998 Corrected by _Reinhard Zumkeller_, Aug 18 2008
%E A072998 Edited by _N. J. A. Sloane_, Mar 31 2021

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