A283871 For all n, the set consisting of the terms {a(1), a(2), a(3), ..., a(n)} has an even number of digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

11, 22, 33, 44, 55, 66, 77, 88, 99, 1001, 1010, 1100, 1111, 1122, 1133, 1144, 1155, 1166, 1177, 1188, 1199, 1212, 1221, 1313, 1331, 1414, 1441, 1515, 1551, 1616, 1661, 1717, 1771, 1818, 1881, 1919, 1991, 2002, 2020, 2112, 2121, 2200, 2211, 2222, 2233, 2244, 2255, 2266, 2277, 2288, 2299, 2323, 2332, 2424, 2442, 2525

Offset: 1

Author

Eric Angelini and Jean-Marc Falcoz, Mar 17 2017

Keywords

• nonn
• base

Comments

The sequence is started with a(1) = 11 and always extended with the smallest integer not yet present and not leading to a contradiction.

Numbers that have an even number of each digit 0 to 9. - Robert Israel, Jan 07 2024

Examples

			The set consisting of the first 15 terms is {11, 22, 33, 44, 55, 66, 77, 88, 99, 1001, 1010, 1100, 1111, 1122, 1133}; we count there six 0's, sixteen 1's, four 2's, four 3's, etc. All those quantities of digits are even numbers.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A283870.

Programs

Maple

filter:= proc(n) local L; L:= convert(n,base,10);
   andmap(t -> numboccur(t,L)::even, L) end proc:
select(filter, [$1..10^4]); # Robert Israel, Jan 07 2024