A098645 List the positions of all digits '1' in the sequence. This is the lexicographically earliest increasing sequence with this property.

1, 3, 10, 20, 22, 31, 32, 33, 34, 35, 41, 51, 52, 53, 54, 55, 111, 112, 200, 210, 220, 222, 231, 1111, 2000, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2020, 2022, 2023, 2024, 2031, 10000, 20000, 20002, 20003, 20004, 20005, 20006, 20007, 20008, 20009

Offset: 1

Author

Eric Angelini, Oct 27 2004

Keywords

• base
• easy
• nonn

Comments

Start with a(1) = 1. For n > 1, choose a(n) to be the smallest number > a(n-1) consistent with the condition that "the a(n)-th digit is a 1 and no 1's occur in other positions" is true for all n.

If we change "> a(n-1)" to "not already used", we get 1, 3, 10, 6, 11, 7, 21, 13, 15, 17, 19, 101, ... - David Wasserman, Feb 26 2008

That sequence has by now been entered as A210415. - M. F. Hasler, Oct 08 2013

Examples

			The first digit of the sequence is a "1", the 3rd digit also, then the 10th, the 11th, etc.
		

Links

• Index to the OEIS: Entries related to self-referencing sequences.

Crossrefs

Cf. A098670. See A114134 for another version. See also A210414-A210423.

Extensions

Entry revised by Eric Angelini and N. J. A. Sloane, Feb 03 2006.

More terms from David Wasserman, Feb 26 2008