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A257794 Lexicographically earliest injective sequence such that a(n) divides a(a(n)) 2
2, 4, 1, 8, 6, 12, 9, 16, 18, 11, 22, 24, 14, 28, 17, 32, 34, 36, 20, 40, 23, 44, 46, 48, 26, 52, 29, 56, 58, 31, 62, 64, 35, 68, 70, 72, 38, 76, 41, 80, 82, 43, 86, 88, 47, 92, 94, 96, 50, 100, 53, 104, 106, 55, 110, 112, 59, 116, 118, 61, 122, 124, 65, 128 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
"Lexicographically earliest injective sequence" means that a(n+1) is the least positive integer not occurring earlier with the given property.
For n>3 it appears that a(n) is either 2*n, n+1 or n+2.
LINKS
E. Angelini, a(n) divides a(a(n)), Seqfan (Apr 11 2015)
EXAMPLE
a(1)=2, a(a(1))=a(2)=4, and 2 divides 4.
a(8)=16, a(a(8))=a(16)=32, and 8 divides 32.
CROSSREFS
Sequence in context: A065290 A065266 A065260 * A345881 A091894 A127151
KEYWORD
nonn
AUTHOR
Eric Angelini and Lars Blomberg, May 11 2015
STATUS
approved

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)