A105647 Lexicographically earliest sequence of increasing numbers whose digits satisfy the "Fractal Jump" rule using only the digits 2 and 5: keep the first digit "d" of the sequence, then jump over the next "d" digits and keep the digit "e" on which you have landed. Jump now over the next "e" digits and keep the digit "f" on which you have landed, etc. The succession "def..." of kept digits is the sequence itself.

2, 5, 25, 52, 55, 222, 252, 255, 552, 555, 2222, 5222, 5252, 5255, 22222, 22252, 22522, 22525, 22555, 25222, 52222, 55222, 55522, 55525, 55552, 55555, 222522, 225222, 225225, 225522, 252222, 252225, 522222, 2225222, 2225252, 2225255, 5222225, 5222522, 5225222

Offset

1,1

Links

Tyler Busby, Table of n, a(n) for n = 1..200

Example

The sequence and the "kept" digits begin
  2, 5, 25, 52, 55, 222, 252, 255, 552, ...
  ^      ^           ^    ^         ^
  2      5           2    5         5

Crossrefs

Cf. A105395, A105396, A105397, A105398.

Sequence in context: A079434 A220170 A273238 * A045586 A137096 A137093

Adjacent sequences: A105644 A105645 A105646 * A105648 A105649 A105650

Keyword

base,easy,nonn

Author

Eric Angelini and Alexandre Wajnberg, May 03 2005

Extensions

Corrected and extended by Tyler Busby, Jan 08 2023

Status

approved