A191598 a(1)=1. Then, if the first n terms contain all the numbers 1 to n, a(n+1)=2*a(n), otherwise a(n+1) is the smallest number not already in the sequence.

1, 2, 4, 3, 6, 5, 10, 7, 8, 9, 18, 11, 12, 13, 14, 15, 16, 17, 34, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 66, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 130

Offset

1,2

Links

Table of n, a(n) for n=1..67.

Example

There are no gaps with just one term, so we double to get a(2)=2. Still no gaps, so we double again to get a(3)=4. Now 3 has not appeared yet, so a(4)=3. The sequence is compact again, so we double to get a(5)=6.

Crossrefs

Sequence in context: A253609 A300002 A082560 * A338221 A283312 A280985

Adjacent sequences: A191595 A191596 A191597 * A191599 A191600 A191601

Keyword

nonn,easy

Author

Greg Knowles, Jun 08 2011

Status

approved