A147870 Number of steps required to erase a finite sequence of nonnegative integers in the following way: at the n-th step, if the last number of the string is 0, delete it; otherwise replace it with n copies of the next-smaller number.

1, 2, 4, 14, 22539988369406

Offset

0,2

Comments

The fifth term is much larger than Skewes's number.

The starting string for a(n) is the length 1 string containing n.

Links

Table of n, a(n) for n=0..4.

Sudoku.com, off-topic, How NOT to erase pencil-marks! [From Martin Chan (martin.chan(AT)westminster.org.uk), Jun 06 2010]

Wikipedia, Skewes's number.

Example

3 is erased in 14 steps:
3->2->11->1000->100->10->1->0000000->000000->00000->0000->000->00->0->x

Crossrefs

Sequence in context: A123052 A064773 A359569 * A347790 A199931 A163361

Adjacent sequences: A147867 A147868 A147869 * A147871 A147872 A147873

Keyword

nonn

Author

Martin Chan (martin.chan(AT)westminster.org.uk), Nov 16 2008

Status

approved