cp's OEIS Frontend

A283870 For all n, the set consisting of the terms {a(1), a(2), a(3), ..., a(n)} has an odd number or 0 of digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

%I A283870 #19 Jan 08 2024 09:03:16
%S A283870 1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99,101,1001,1010,1100,1111,
%T A283870 1122,1133,1144,1155,1166,1177,1188,1199,1212,1221,1313,1331,1414,
%U A283870 1441,1515,1551,1616,1661,1717,1771,1818,1881,1919,1991,2002,2020,2112,2121,2200,2211,2222,2233,2244,2255,2266,2277,2288
%N A283870 For all n, the set consisting of the terms {a(1), a(2), a(3), ..., a(n)} has an odd number or 0 of digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.
%C A283870 The sequence is started with a(1) = 1 and always extended with the smallest integer not yet present and not leading to a contradiction.
%H A283870 Robert Israel, <a href="/A283870/b283870.txt">Table of n, a(n) for n = 1..10000</a>
%F A283870 a(n) = A283871(n-10) for n >= 20. - _Robert Israel_, Jan 07 2024
%e A283870 The set consisting of the first 20 terms is {1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99,101,1001}; we count three 0's, seven 1's, three 2's, three 3's, three 4's, etc. All those quantities of digits are odd numbers.
%p A283870 filter:= proc(n) local L; L:= convert(n,base,10);
%p A283870    andmap(t -> numboccur(t,L)::even, L) end proc:
%p A283870 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, op(select(filter, [$1000..9999])); # _Robert Israel_, Jan 07 2024
%Y A283870 Cf. A283871.
%K A283870 nonn,base
%O A283870 1,2
%A A283870 _Eric Angelini_ and _Jean-Marc Falcoz_, Mar 17 2017
%E A283870 Definition corrected by _Robert Israel_, Jan 07 2024