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A340377 Numbers k such that there are no 2-digits in the ternary expansion of A048673(k).

%I A340377 #13 Jan 16 2021 06:39:02
%S A340377 1,3,5,9,13,17,19,21,35,47,53,59,67,71,73,91,93,95,121,123,129,143,
%T A340377 145,157,163,173,175,179,207,211,229,233,239,255,267,291,297,299,321,
%U A340377 327,351,355,371,381,405,413,437,451,477,479,485,487,499,503,505,523,527,541,547,549,557,595,643,645,647,661,691,701
%N A340377 Numbers k such that there are no 2-digits in the ternary expansion of A048673(k).
%C A340377 All terms are odd, because A048673(2n) = 3*A048673(n) - 1, which forces the least significant digit in the ternary expansion of A048673(2n) to be "2".
%H A340377 Antti Karttunen, <a href="/A340377/b340377.txt">Table of n, a(n) for n = 1..20000</a>
%H A340377 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%o A340377 (PARI)
%o A340377 A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961
%o A340377 A048673(n) = (A003961(n)+1)/2;
%o A340377 A289814(n) = { my (d=digits(n, 3)); fromdigits(vector(#d, i, if (d[i]==2, 1, 0)), 2); } \\ From A289814
%o A340377 A291759(n) = A289814(A048673(n));
%o A340377 isA340377(n) = (0==A291759(n));
%Y A340377 Positions of zeros in A291759 and in A340379. Positions of ones in A340382.
%Y A340377 Cf. A048673, A340376.
%K A340377 nonn
%O A340377 1,2
%A A340377 _Antti Karttunen_, Jan 15 2021