A257794 Lexicographically earliest injective sequence such that a(n) divides a(a(n)).

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

Offset: 1

Author

Eric Angelini and Lars Blomberg, May 11 2015

Keywords

• nonn

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.

Examples

			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.
		

Links

• Lars Blomberg, Table of n, a(n) for n = 1..9999
• E. Angelini, a(n) divides a(a(n)), Seqfan (Apr 11 2015)