%I
%S 1,0,5,7,6,2,4,3,17,19,18,23,25,24,20,22,21,8,10,9,14,16,15,11,13,12,
%T 53,55,54,59,61,60,56,58,57,71,73,72,77,79,78,74,76,75,62,64,63,68,70,
%U 69,65,67,66,26,28,27,32,34,33,29,31,30,44,46,45,50,52,51,47,49,48,35
%N Tersum n + (n1); write n and n1 in base 3 and add mod 3 with no carries.
%e a(21)=14 since 21 and 20 are written in base 3 as 210 and 202 and so their tersum is 112 in base 3, i.e. 9+3+2=14.
%Y Cf. A004482, A004488, A004489, A038712.
%K nonn
%O 1,3
%A _Henry Bottomley_, Jan 22 2001
