A337132 a(n) is the number of squares at distance n from the central square of a Vicsek fractal.

1, 4, 4, 4, 12, 4, 4, 12, 4, 4, 12, 12, 12, 36, 4, 4, 12, 4, 4, 12, 12, 12, 36, 4, 4, 12, 4, 4, 12, 12, 12, 36, 12, 12, 36, 12, 12, 36, 36, 36, 108, 4, 4, 12, 4, 4, 12, 12, 12, 36, 4, 4, 12, 4, 4, 12, 12, 12, 36, 12, 12, 36, 12, 12, 36, 36, 36, 108, 4, 4, 12

Offset

0,2

Comments

For symmetry reasons, a(n) is a multiple of 4 for any n > 0.

Links

Rémy Sigrist, Table of n, a(n) for n = 0..6561

Rémy Sigrist, Illustration of initial terms

Rémy Sigrist, PARI program for A337132

Wikipedia, Vicsek fractal

Formula

a(n) = 4 iff n belongs to A153775.

Prog

(PARI) See Links section.

Crossrefs

See A337018 for similar sequences.

Cf. A153775.

Sequence in context: A220931 A219578 A219373 * A151906 A151896 A267191

Adjacent sequences: A337129 A337130 A337131 * A337133 A337134 A337135

Keyword

nonn

Author

Rémy Sigrist, Nov 21 2020

Status

approved