A331349 Fill an infinite square array by following a spiral around the origin; if the square at position (x, y) is empty then set either T(x, y) = 1 or T(x, y) = T(2*x, 2*y) = 2 such that the RUNS transform of the sequence of values as they are chosen equals the sequence of values as they are visited; first choose the value 1. This sequence corresponds to the values as they are chosen.

1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1

Offset

0,2

Links

Table of n, a(n) for n=0..86.

Rémy Sigrist, PARI program for A331349

Example

The first values can be found alongside this spiral:
      1---2---1---1---2---1---1
      |                       |
      1   2---1---1---2---+   2
      |   |               |   |
      2   1   1---1---2   2   1
      |   |   |       |   |   |
      2   |   2   1---2   |   2
      |   |   |           |   |
      1   1   1---2---2---1   2
      |   |                   |
      1   2---2-------1-------1
      |
      2---1---1---2---1---1---2 ...

Prog

(PARI) See Links section.

Crossrefs

See A331348 for the sequence of values as they are visited.

Sequence in context: A351617 A074293 A013949 * A078880 A000002 A074295

Adjacent sequences: A331346 A331347 A331348 * A331350 A331351 A331352

Keyword

nonn

Author

Rémy Sigrist, Jan 14 2020

Status

approved