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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. 0
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 (list; graph; refs; listen; history; text; internal format)
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 * A283312 A280985 A127202

Adjacent sequences:  A191595 A191596 A191597 * A191599 A191600 A191601

KEYWORD

nonn,easy

AUTHOR

Greg Knowles, Jun 08 2011

STATUS

approved

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Last modified July 22 05:47 EDT 2019. Contains 325213 sequences. (Running on oeis4.)