|
%I #14 Jun 26 2021 09:18:23
%S 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 32,33,34,35,36,37,40,41,42,45,46,47,50,51,52,53,54,55,56,57,58,59,60,
%U 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 Numbers k such that base 5 expansion matches (0|1|2)*((0|1)(3|4))?(0|1|2)*
%C 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 <a href="/index/Ar#5-automatic">Index entries for 5-automatic sequences</a>.
%o (Perl) sub conv_x_base_n { my($x,$b) = @_; my ($r,$z) = (0,'');
%o do { $r = $x % $b; $x = ($x - $r)/$b; $z = "$r" . $z; } while(0 != $x);
%o return($z); }
%o 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 Cf. A037453, A046097, A050608, A051382.
%K nonn,easy,base
%O 1,3
%A _Antti Karttunen_, Oct 24 1999
%E a(1)=0 inserted by _Georg Fischer_, Jun 26 2021
|
