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A225773 The squares on a chessboard that are black, counting from top left corner and down. 1
2, 4, 6, 8, 9, 11, 13, 15, 18, 20, 22, 24, 25, 27, 29, 31, 34, 36, 38, 40, 41, 43, 45, 47, 50, 52, 54, 56, 57, 59, 61, 63 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

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

FORMULA

a(1) = 2

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

MATHEMATICA

sqColor[n_] := Mod[n, 2] + (1 - 2*Mod[n, 2])*Mod[Floor[(n - 1)/8], 2]; Select[Range[64], sqColor[#] == 0 &]

CROSSREFS

Cf. A225240 (white-squares sequence).

Sequence in context: A215000 A228246 A184587 * A233671 A143346 A189010

Adjacent sequences:  A225770 A225771 A225772 * A225774 A225775 A225776

KEYWORD

nonn,easy,fini,full

AUTHOR

Jonas Hallgren, Jul 26 2013

STATUS

approved

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Last modified April 6 11:51 EDT 2020. Contains 333273 sequences. (Running on oeis4.)