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

Author

Leroy Quet, May 31 2010

Keywords

• nonn

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

Extensions

More terms from Sean A. Irvine, Jun 14 2011