%I A004488
%S A004488 0,2,1,6,8,7,3,5,4,18,20,19,24,26,25,21,23,22,9,11,10,15,
%T A004488 17,16,12,14,13,54,56,55,60,62,61,57,59,58,72,74,73,78,
%U A004488 80,79,75,77,76,63,65,64,69,71,70,66,68,67,27,29,28,33
%N A004488 Tersum n + n.
%C A004488 Could also be described as "Write n in base 3, then replace each digit 
               by its base 3 negative" as with A048647 for base 4 - Henry Bottomley 
               (se16(AT)btinternet.com), Apr 19 2000
%C A004488 a(a(n)) = n, a self-inverse permutation of natural numbers. - Reinhard 
               Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 19 2003
%H A004488 <a href="Sindx_Per.html#IntegerPermutation">Index entries for sequences 
               that are permutations of the natural numbers</a>
%F A004488 Tersum m + n: write m and n in base 3 and add mod 3 with no carries, 
               e.g. 5 + 8 = "21" + "22" = "10" = 1.
%F A004488 a(n) = Sum(3-d(i)-3*0^d(i): n=Sum(d(i)*3^d(i): 0<=d(i)<3)); - Reinhard 
               Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 19 2003
%Y A004488 Sequence in context: A026220 A138750 A048850 this_sequence A011419 A011133 
               A073675
%Y A004488 Adjacent sequences: A004485 A004486 A004487 this_sequence A004489 A004490 
               A004491
%K A004488 nonn
%O A004488 0,2
%A A004488 N. J. A. Sloane (njas(AT)research.att.com).