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A225240 The squares on a chessboard that are white, counting from top left corner and down. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A189372 A108052 A046868 * A104309 A184586 A190511

Adjacent sequences:  A225237 A225238 A225239 * A225241 A225242 A225243

KEYWORD

nonn,fini,full,easy

AUTHOR

Jonas Hallgren, Jul 25 2013

STATUS

approved

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Last modified November 14 06:14 EST 2018. Contains 317162 sequences. (Running on oeis4.)