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A242399 Write n and 3n in ternary representation and add all trits modulo 3.

%I A242399 #13 Feb 16 2025 08:33:22
%S A242399 0,4,8,12,16,11,24,19,23,36,40,44,48,52,47,33,28,32,72,76,80,57,61,56,
%T A242399 69,64,68,108,112,116,120,124,119,132,127,131,144,148,152,156,160,155,
%U A242399 141,136,140,99,103,107,84,88,83,96,91,95,216,220,224,228,232
%N A242399 Write n and 3n in ternary representation and add all trits modulo 3.
%H A242399 Reinhard Zumkeller, <a href="/A242399/b242399.txt">Table of n, a(n) for n = 0..10000</a>
%H A242399 P. Mathonet, M. Rigo, M. Stipulanti and N. Zénaïdi, <a href="https://arxiv.org/abs/2201.06636">On digital sequences associated with Pascal's triangle</a>, arXiv:2201.06636 [math.NT], 2022.
%H A242399 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Ternary.html">Ternary.</a>
%H A242399 Wikipedia, <a href="http://en.wikipedia.org/wiki/Ternary_numeral_system">Ternary numeral system</a>
%H A242399 <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>
%F A242399 a(n) <= 4*n; a(m) = 4*m iff m is a term of A242407.
%F A242399 a(n) = A008586(n) - A242400(n).
%e A242399 n = 25, 3*n = 75:
%e A242399 .  A007089(25) =  221
%e A242399 .  A007089(75) = 2210
%e A242399 .   add trits    ----
%e A242399 .    modulo 3    2101 = A007089(64), hence a(25) = 64.
%o A242399 (Haskell)
%o A242399 a242399 n = foldr (\t v -> 3 * v + t) 0 $
%o A242399                   map (flip mod 3) $ zipWith (+) ([0] ++ ts) (ts ++ [0])
%o A242399             where ts = a030341_row n
%Y A242399 Cf. A004488, A007089, A008586, A030341, A048724, A242400, A242407.
%Y A242399 Row / column 4 of A325820.
%K A242399 nonn,base
%O A242399 0,2
%A A242399 _Reinhard Zumkeller_, May 13 2014