A090239 a(n) = A053838(n) + 2 modulo 3.

2, 0, 1, 0, 1, 2, 1, 2, 0, 0, 1, 2, 1, 2, 0, 2, 0, 1, 1, 2, 0, 2, 0, 1, 0, 1, 2, 0, 1, 2, 1, 2, 0, 2, 0, 1, 1, 2, 0, 2, 0, 1, 0, 1, 2, 2, 0, 1, 0, 1, 2, 1, 2, 0, 1, 2, 0, 2, 0, 1, 0, 1, 2, 2, 0, 1, 0, 1, 2, 1, 2, 0, 0, 1, 2, 1, 2, 0, 2, 0, 1, 0, 1, 2, 1, 2, 0, 2, 0, 1, 1, 2, 0, 2, 0, 1, 0, 1, 2, 2, 0, 1, 0, 1, 2

Offset: 0

Author

Philippe Deléham, Feb 04 2004

Keywords

• nonn

Comments

Can construct sequence by starting with 2 and mapping 0->012, 1->120, 2->201 (e.g., 2, 201, 201012120, ...) and looking at n-th digit of a term with sufficient digits.

Links

• Paolo Xausa, Table of n, a(n) for n = 0..19682

Crossrefs

Cf. A053838, A090193.

Programs

Mathematica

First[SubstitutionSystem[{0 -> {0, 1, 2}, 1 -> {1, 2, 0}, 2 -> {2, 0, 1}}, 2, {5}]] (* Paolo Xausa, Mar 17 2025 *)

PARI

a(n)=if(n<0,0,2*(n==0),(n+a(n\3))%3) /* Michael Somos, Feb 14 2004 */

Formula

a(n) = mod(n+a([n/3]), 3), a(0)=2. - Michael Somos, Feb 14 2004