

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
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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(n1) + 2 + (mod(a(n1)+1, 8) == 0)  (mod(a(n1), 8) == 0).
To check if n is white: mod(s, 2) + (1  2*mod(s, 2)) * mod(floor((s1)/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 (blacksquares 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



