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%I #13 Jul 20 2020 01:59:19
%S 0,1,1,4,4,4,4,13,13,13,13,13,13,13,13,40,40,40,40,40,40,40,40,40,40,
%T 40,40,40,40,40,40,121,121,121,121,121,121,121,121,121,121,121,121,
%U 121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121
%N Repeating k-th ternary repunit (A003462) 2^k times, k >= 0.
%C a(n) is the greatest ternary repunit that is not greater than the n-th number with no 2 in ternary representation.
%F A032924(n) = a(n) + A107681(n);
%F A081604(A107681(n)) <= A081604(a(n)) = A081604(A032924(n)) = A000523(n+1).
%F a(n) = A003462(A000523(n+1)).
%e k=1: A003462(1) = (3^1-1)/2 = 1, therefore a(1) = a(2^1) = 1;
%e k=2: A003462(2) = (3^2-1)/2 = 4, therefore a(2+1) = a(2+2) =
%e a(2+3) = a(2+2^2) = 4.
%t With[{nn=5},Flatten[Table[#[[1]],{#[[2]]}]&/@Thread[{Table[FromDigits[ PadRight[{},n,1],3],{n,nn}],2^Range[nn]}]]] (* _Harvey P. Dale_, Jan 04 2013 *)
%o (PARI) apply( {A107680(n)=3^exponent(n+1)\2}, [0..66]) \\ _M. F. Hasler_, Jun 22 2020
%Y Cf. A007089, A003462 (repunits in base 3), A000523 (number of digits in binary representation of n).
%K nonn
%O 0,4
%A _Reinhard Zumkeller_, May 20 2005
%E Corrected by _T. D. Noe_, Oct 25 2006
%E Extended to a(0) = 0 by _M. F. Hasler_, Jun 23 2020
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