A210421 List the positions of all digits 7 in the concatenation of all terms, not necessarily in order. This is the lexicographically earliest such sequence.

2, 7, 4, 70, 8, 77, 11, 71, 15, 72, 19, 73, 23, 74, 27, 75, 26, 33, 76, 37, 78, 36, 43, 79, 47, 700, 46, 54, 701, 59, 702, 64, 703, 69, 777, 7777, 77770, 83, 704, 87, 90, 705, 95, 706, 101, 707, 103, 110, 708, 116, 709, 122, 710, 127, 131, 711, 137, 712, 136

Offset: 1

Author

Paolo P. Lava, Mar 26 2012

Keywords

• nonn
• base

Comments

See A210415 for comments, links, and code.

Examples

			The sequence cannot start with 1 because the first digit is not 7. Let us start with 2: the second digit is equal to 7. The third digit cannot be 3 because the third digit is not 7. So let it be 4. In the next position we now have 70 because it is the minimum number greater than 7 and starting with the digit 7. And so on.
		

Links

• Danny Rorabaugh, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A210414, A210415, A210416, A210417, A210418, A210419, A210420, A210422, A210423.

Extensions

Name edited and a(5)-a(31) corrected by Danny Rorabaugh, Nov 30 2015