A131393 Conjectured permutation of the positive integers using Rule 2 with a(1)=1.

1, 2, 4, 3, 6, 10, 8, 5, 11, 7, 12, 19, 14, 22, 16, 9, 18, 28, 20, 31, 21, 33, 24, 13, 26, 40, 27, 42, 30, 15, 32, 48, 34, 17, 35, 54, 38, 58, 39, 60, 37, 59, 41, 64, 44, 23, 47, 25, 50, 76, 52, 79, 53, 81, 56, 29, 61, 90, 62, 92, 63, 94, 57, 91, 55, 88, 49, 84, 51, 87, 46, 83

Offset

1,2

Comments

Conjecture 1: a( ) is a permutation of the positive integers. Conjecture 2: d( ) is a permutation of the integers. The sequence using Rule 1 ("negative before positive") is A131388.

This sequence was generated using "Rule 2" in a computer program which been lost. The wording of "Rule 2" in the Formula section, although flawed, is retained in case someone can rediscover "Rule 2" and contribute a corrected version. - Clark Kimberling, May 18 2015

Links

Table of n, a(n) for n = 1..72

Formula

The following version of "Rule 2" is defective; see Comments. - Clark Kimberling, May 18 2015

Rule 2 ("positive before negative"): define sequences d( ) and a( ) as follows: d(1)=0, a(1)=1 and for n>=2, d(n) is the least positive integer d such that a(n-1)+d is not among a(1), a(2),...,a(n-1), or, if no such d exists, then d(n) is the greatest negative integer d such that a(n-1)+d is not among a(1), a(2),...,a(n-1). Then a(n)=a(n-1)+d.

Example

a(2)=1+1, a(3)=a(2)+2, a(4)=a(3)+(-1), a(5)=a(4)+3, a(6)=a(5)+4.
The first term that differs from A131388 is a(28)=42.

Crossrefs

Cf. A131388, A131389, A131390, A131391, A131392, A131394, A131395, A131396, A131397.

Sequence in context: A327120 A377837 A131388 * A216476 A002326 A285493

Adjacent sequences: A131390 A131391 A131392 * A131394 A131395 A131396

Keyword

nonn,unkn

Author

Clark Kimberling, Jul 05 2007

Status

approved