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 A050607 #16 Jun 01 2025 22:09:35
%S A050607 0,1,2,3,4,5,6,7,8,9,10,11,12,15,16,17,20,21,22,25,26,27,28,29,30,31,
%T A050607 32,33,34,35,36,37,40,41,42,45,46,47,50,51,52,53,54,55,56,57,58,59,60,
%U A050607 61,62,75,76,77,80,81,82,85,86,87,100,101,102,105,106,107,110,111,112,125,126,127,128,129,130,131,132,133,134,135,136,137,140,141,142,145
%N A050607 Numbers k such that base 5 expansion matches (0|1|2)*((0|1)(3|4))?(0|1|2)*.
%C A050607 25 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 A050607 <a href="/index/Ar#5-automatic">Index entries for 5-automatic sequences</a>.
%o A050607 (Perl) sub conv_x_base_n { my($x,$b) = @_; my ($r,$z) = (0,'');
%o A050607 do { $r = $x % $b; $x = ($x - $r)/$b; $z = "$r" . $z; } while(0 != $x);
%o A050607 return($z); }
%o A050607 for($i=0; $i <= 201; $i++) { if(("0" . conv_x_base_n($i,5)) =~ /^(0|1|2)*((0|1)(3|4))?(0|1|2)*$/) { print $i, ","; } }
%Y A050607 Cf. A037453, A046097, A050608, A051382.
%K A050607 nonn,easy,base
%O A050607 1,3
%A A050607 _Antti Karttunen_, Oct 24 1999
%E A050607 a(1)=0 inserted by _Georg Fischer_, Jun 26 2021