A225240 The squares on a chessboard that are white, counting from top left corner and down.

1, 3, 5, 7, 10, 12, 14, 16, 17, 19, 21, 23, 26, 28, 30, 32, 33, 35, 37, 39, 42, 44, 46, 48, 49, 51, 53, 55, 58, 60, 62, 64

Offset

1,2

Comments

Equivalently it represents the squares that are black, counting from bottom left corner and up.

Links

Table of n, a(n) for n=1..32.

Formula

a(1) = 1, a(n) = a(n-1) + 2 + (mod(a(n-1)+1, 8) == 0) - (mod(a(n-1), 8) == 0).

To check if n is white: mod(s, 2) + (1 - 2*mod(s, 2)) * mod(floor((s-1)/8), 2).

Mathematica

sqColor[n_] := Mod[n, 2] + (1 - 2*Mod[n, 2])*Mod[Floor[(n - 1)/8], 2]; Select[Range[64], sqColor[#] == 1 &]

Crossrefs

Cf. A225773 (black-squares sequence).

Sequence in context: A108052 A359113 A046868 * A104309 A306683 A184586

Adjacent sequences: A225237 A225238 A225239 * A225241 A225242 A225243

Keyword

nonn,fini,full,easy

Author

Jonas Hallgren, Jul 25 2013

Status

approved