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%I #18 Jun 26 2021 09:18:36
%S 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,28,
%T 29,30,31,35,36,37,38,42,43,44,45,49,50,51,52,53,54,55,56,57,58,59,60,
%U 61,62,63,64,65,66,67,68,69,70,71,72,73,77,78,79,80,84,85,86,87,91,92,93,94,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113
%N Numbers k such that base 7 expansion matches (0|1|2|3)*((0|1|2)(4|5|6))?(0|1|2|3)*
%C 49 does not divide C(2s-1,s) = A001700(s) (nor C(2s,s) = A000984(s), central column of Pascal's triangle) if and only if s is one of the terms in this sequence.
%H <a href="/index/Ar#7-automatic">Index entries for 7-automatic sequences</a>.
%o (Perl) # For conv_x_base_n function, see A050607.
%o for($i=0; $i <= 1000; $i++) { if(("0" . conv_x_base_n($i,7)) =~ /^(0|1|2|3)*((0|1|2)(4|5|6))?(0|1|2|3)*$/) { print $i, ","; } }
%Y Cf. A037461, A046097, A050607, A051382.
%K nonn,easy,base
%O 1,3
%A _Antti Karttunen_, 1999
%E a(1)=0 inserted by _Georg Fischer_, Jun 26 2021