A257862 a(n) = n if n <= 3, otherwise a(n) is the smallest number not already used and relatively prime to a(n-1) such that the set of prime divisors of one of the numbers {a(n-2), a(n)} is a subset of the set of prime divisors of the other.

1, 2, 3, 4, 9, 8, 15, 14, 5, 7, 10, 21, 16, 27, 20, 33, 25, 11, 30, 77, 6, 49, 12, 35, 18, 125, 24, 55, 32, 121, 26, 99, 13, 66, 65, 22, 169, 44, 39, 64, 81, 28, 45, 56, 75, 98, 135, 112, 165, 128, 225, 34, 105, 17, 63, 68, 147, 136, 189, 170, 231, 40, 243, 50

Offset: 1

Author

Vladimir Shevelev, May 11 2015

Keywords

• nonn

Comments

The sequence is an analog of the Yellowstone sequence A098550 with a more stringent condition on neighboriong terms at distance 2. However, we conjecture that, as with A098550, this is a permutation of the positive integers.

By definition, every pair of neighboring terms at distance 2 are strictly connected numbers as defined in comment in A257112.

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A098550, A257112, A255348.

Extensions

More terms from Peter J. C. Moses, May 11 2015