A210419 List the positions of all digits 5 in the concatenation of all terms, not necessarily in order. This is the lexicographically earliest such sequence.
2, 5, 4, 55, 7, 50, 11, 51, 15, 52, 14, 21, 53, 25, 54, 24, 31, 56, 35, 57, 34, 41, 58, 45, 59, 44, 65, 555, 5555, 550, 63, 505, 68, 500, 73, 501, 78, 502, 83, 503, 88, 504, 93, 506, 98, 507, 104, 508, 110, 509, 115, 119, 510, 125, 511, 124, 134, 512, 140, 513
Offset: 1
Examples
The sequence cannot start with 1 because the first digit is not 5. Let us start with 2: the second digit is equal to 5. The third digit cannot be 3 because the third digit is not 5. So let it be 4. The next term must begin with a 5 because 4 is already in the sequence. Since 5 is also a previous term, it must be 55. With 2,4,5 already used, and 1,3,6 pointing at digits that are not 5, the next term must be 7.
Links
- Danny Rorabaugh, Table of n, a(n) for n = 1..1000
Extensions
a(5)-a(90) corrected by Danny Rorabaugh, Nov 27 2015
Comments