This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A050608 #20 Jun 01 2025 22:09:49
%S A050608 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 A050608 29,30,31,35,36,37,38,42,43,44,45,49,50,51,52,53,54,55,56,57,58,59,60,
%U A050608 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 A050608 Numbers k such that base 7 expansion matches (0|1|2|3)*((0|1|2)(4|5|6))?(0|1|2|3)*.
%C A050608 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 A050608 <a href="/index/Ar#7-automatic">Index entries for 7-automatic sequences</a>.
%o A050608 (Perl) # For conv_x_base_n function, see A050607.
%o A050608 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 A050608 Cf. A037461, A046097, A050607, A051382.
%K A050608 nonn,easy,base
%O A050608 1,3
%A A050608 _Antti Karttunen_, 1999
%E A050608 a(1)=0 inserted by _Georg Fischer_, Jun 26 2021