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%I #10 Sep 08 2022 08:46:11
%S 6,7,66,67,76,77,666,667,676,677,766,767,776,777,6666,6667,6676,6677,
%T 6766,6767,6776,6777,7666,7667,7676,7677,7766,7767,7776,7777,66666,
%U 66667,66676,66677,66766,66767,66776,66777,67666,67667
%N Numbers which have only digits 6 and 7 in base 10.
%H Vincenzo Librandi, <a href="/A256292/b256292.txt">Table of n, a(n) for n = 1..8190</a>
%H <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%F a(n) = A007931(n) + A002279(A000523(n+1)) = A256291(n) + A256077(n) etc.
%t Flatten[Table[FromDigits[#,10]&/@Tuples[{6,7},n],{n,5}]]
%o (Magma) [n: n in [1..35000] | Set(IntegerToSequence(n, 10)) subset {7, 6}];
%o (PARI) A256292(n)=vector(#n=binary(n+1)[2..-1],i,10^(#n-i))*n~+10^#n\9*6
%o (Magma) [n: n in [1..100000] | Set(Intseq(n)) subset {6,7}]; // _Vincenzo Librandi_, Aug 19 2016
%Y Cf. A007088 (digits 0 & 1), A007931 (digits 1 & 2), A032810 (digits 2 & 3), A032834 (digits 3 & 4), A256290 (digits 4 & 5), A256291 (digits 5 & 6), A256340 (digits 7 & 8), A256341 (digits 8 & 9).
%K nonn,base,easy
%O 1,1
%A _M. F. Hasler_, Mar 27 2015
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