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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 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 A306683 A184586 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 September 22 19:36 EDT 2021. Contains 347608 sequences. (Running on oeis4.)