A393564 a(n) is the number of unit squares in the square lattice, divided by 8, that have 2 vertices strictly inside and 2 vertices strictly outside the circle x^2 + y^2 = n.

0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 2, 2, 1, 0, 1, 2, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 2, 2, 2, 3, 2, 3, 2, 1, 2, 2, 1, 2, 3, 3, 3, 2, 3, 3, 3, 2, 1, 3, 2, 2, 3, 3, 3, 3, 2, 3, 3, 3, 4, 4, 3, 1, 3, 3, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 3, 3, 2, 3, 3, 2, 4, 4, 4, 3, 3

Offset

0,15

Links

Hugo Pfoertner, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A004018, A014200, A057655, A393562.

Sequence in context: A208568 A193804 A180424 * A092339 A079693 A117444

Adjacent sequences: A393561 A393562 A393563 * A393565 A393566 A393567

Keyword

nonn

Author

Hugo Pfoertner, Feb 25 2026

Status

approved