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

1,2

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.

Sequence in context: A256224 A340783 A255509 * A350359 A340807 A329449

Adjacent sequences: A257859 A257860 A257861 * A257863 A257864 A257865

Keyword

nonn

Author

Vladimir Shevelev, May 11 2015

Extensions

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

Status

approved