A175502 a(1) = 1. a(n) = the smallest integer not yet occurring such that each unordered pair {d(a(k)),d(a(k-1))} occurs only once at most, for 2<= k <= n, where d(m) = the number of divisors of m.

1, 2, 3, 4, 6, 5, 12, 8, 10, 16, 7, 24, 9, 18, 20, 30, 14, 36, 11, 48, 15, 60, 13, 64, 21, 120, 17, 144, 22, 180, 19, 192, 25, 49, 72, 28, 80, 40, 42, 81, 32, 100, 54, 84, 90, 112, 121, 168, 44, 240, 23, 360, 26, 320, 45, 252, 56, 210, 96, 196

Offset

1,2

Comments

This sequence seems likely to be a permutation of the positive integers. Is it?

Links

Ivan Neretin, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A175500, A175503

Sequence in context: A075160 A119755 A206710 * A364246 A368133 A362855

Adjacent sequences: A175499 A175500 A175501 * A175503 A175504 A175505

Keyword

nonn

Author

Leroy Quet, May 31 2010

Extensions

More terms from Sean A. Irvine, Jun 14 2011

Status

approved