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%I #9 Jul 09 2024 02:21:41
%S 0,1,1,3,4,4,3,4,4,9,10,10,12,13,13,12,13,13,9,10,10,12,13,13,12,13,
%T 13,27,28,28,30,31,31,30,31,31,36,37,37,39,40,40,39,40,40,36,37,37,39,
%U 40,40,39,40,40,27,28,28,30,31,31,30,31,31,36,37,37,39,40
%N a(n) is the greatest term t <= n of A005836 such that n - t also belongs to A005836.
%C To compute a(n): in the ternary expansion of n, 2's by 1's.
%H Rémy Sigrist, <a href="/A374363/b374363.txt">Table of n, a(n) for n = 0..6560</a>
%F a(n) = T(n, A120880(k)-1).
%F a(n) = n - A374362(n).
%F a(n) <= n with equality iff n belongs to A005836.
%F a(n) = A005836(1+A289831(n)).
%e The first terms, in decimal and in ternary, are:
%e n a(n) ter(n) ter(a(n))
%e -- ---- ------ ---------
%e 0 0 0 0
%e 1 1 1 1
%e 2 1 2 1
%e 3 3 10 10
%e 4 4 11 11
%e 5 4 12 11
%e 6 3 20 10
%e 7 4 21 11
%e 8 4 22 11
%e 9 9 100 100
%e 10 10 101 101
%e 11 10 102 101
%e 12 12 110 110
%e 13 13 111 111
%e 14 13 112 111
%e 15 12 120 110
%o (PARI) a(n) = fromdigits(apply(d -> [0, 1, 1][1+d], digits(n, 3)), 3)
%Y Cf. A005836, A120880, A289831, A374361, A374362.
%K nonn,base
%O 0,4
%A _Rémy Sigrist_, Jul 06 2024
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