A287404 Positions of 2 in A287401.

3, 4, 8, 11, 13, 18, 19, 23, 27, 28, 32, 36, 38, 40, 45, 48, 49, 53, 56, 58, 63, 64, 68, 72, 75, 76, 80, 83, 85, 90, 91, 95, 99, 102, 103, 107, 109, 113, 117, 119, 121, 126, 129, 130, 134, 138, 139, 143, 146, 148, 153, 154, 158, 162, 163, 167, 171, 173, 175

Offset: 1

Author

Clark Kimberling, May 25 2017

Keywords

• nonn
• easy

Comments

a(n) - a(n-1) is in {1, 2, 3, 4, 5} for n >= 1; also, 3n - a(n) is in {0, 1, 2} for n >= 1. The first 20 numbers 3n - a(n) are 0, 2, 1, 1, 2, 0, 2, 1, 0, 2, 1, 0, 1, 2, 0, 0, 2, 1, 1, 2, with 0 in positions given by A189728.

Links

• Clark Kimberling, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A287401, A287403, A287404.

Programs

Mathematica

s = Nest[Flatten[# /. {0->{0, 1, 2}, 1->{2, 1, 0}, 2->{1, 2, 0}}] &, {0}, 9]; (*A287401*)
Flatten[Position[s, 0]]; (*A189728*)
Flatten[Position[s, 1]]; (*A287403*)
Flatten[Position[s, 2]]; (*A287404*)