cp's OEIS Frontend

A105391 Numbers m such that there are an equal number of numbers <= m that are contained and that are not contained in the concatenation of terms <= m in A048991.

%I A105391 #10 Jul 19 2016 11:04:54
%S A105391 740,1260,1262,5230,15804,15814,15816,36294,194876,213868
%N A105391 Numbers m such that there are an equal number of numbers <= m that are contained and that are not contained in the concatenation of terms <= m in A048991.
%C A105391 A105390(a(n)) = a(n)/2.
%C A105391 There are no other terms <= 600000. The plots in a105390.gif strongly suggest that the sequence is complete. - _Klaus Brockhaus_, Aug 15 2007
%H A105391 Nick Hobson, <a href="/A105391/a105391.py.txt">Python program for this sequence</a>
%e A105391 A105390(n) < n/2 for n < a(1)=740;
%e A105391 A105390(n) > n/2 for n with 740 < n < a(2)=1260;
%e A105391 A105390(1261)=631, A105390(a(3))=A105390(1262)=631;
%e A105391 A105390(n) < n/2 for n with 1262 < n < a(4)=5230;
%e A105391 A105390(n) > n/2 for n with 5230 < n < a(5)=15804;
%e A105391 A105390(n) < n/2 for n with 15804 < n < a(6)=15814;
%e A105391 A105390(15815)=7908, A105390(a(7))=A105390(15816)=7909;
%e A105391 A105390(n) < n/2 for n with 15816 < n < a(8)=36294;
%e A105391 A105390(n) > n/2 for n with 36294 < n < a(9)=194876; etc.
%o A105391 (JBASIC)
%o A105391 s$ = "" : c = 0 : d = 0
%o A105391 FOR n = 1 TO 40000
%o A105391 sn$ = str$(n)
%o A105391 IF instr(s$, sn$) > 0 THEN d = d+1 ELSE c = c+1 : s$ = s$ + sn$
%o A105391 IF c = d THEN print n ; "," ;
%o A105391 NEXT ' _Klaus Brockhaus_, Aug 15 2007
%Y A105391 Cf. A048991, A048992, A105390, A131982 (numbers n such that A131981(n) = n/2).
%K A105391 nonn,base,more
%O A105391 1,1
%A A105391 _Reinhard Zumkeller_, Apr 04 2005