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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
OFFSET
1,1
COMMENTS
Equivalently it represents the squares that are white, counting from bottom left corner and up.
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: A228246 A184587 A345436 * A233671 A348854 A143346
KEYWORD
nonn,easy,fini,full
AUTHOR
Jonas Hallgren, Jul 26 2013
STATUS
approved