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

Author

Rémy Sigrist, Nov 21 2020

Keywords

• nonn

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

Crossrefs

See A337018 for similar sequences.

Cf. A153775.

Programs

PARI

See Links section.

Formula

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