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

1,1

Comments

See A210415 for comments, links, and code.

Links

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

Example

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.

Crossrefs

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

Sequence in context: A013623 A345273 A348145 * A326098 A198672 A306767

Adjacent sequences: A210418 A210419 A210420 * A210422 A210423 A210424

Keyword

nonn,base

Author

Paolo P. Lava, Mar 26 2012

Extensions

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

Status

approved