

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
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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(n1) + 2 + (mod(a(n1)+1, 8) == 0)  (mod(a(n1), 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 (whitesquares 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



