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 A303646 a(n) is the number of lattice points in a Cartesian grid between a square with integer sides 2*n and its inscribed circle. The sides of the square are parallel to the bisector of coordinate axes. 4
 0, 0, 12, 12, 32, 32, 32, 68, 60, 104, 104, 104, 156, 148, 216, 216, 300, 292, 276, 368, 368, 468, 460, 452, 560, 544, 676, 668, 816, 792, 784, 932, 916, 1080, 1048, 1048, 1220, 1212, 1384, 1360, 1352, 1556, 1532, 1736, 1704, 1956, 1924, 1900, 2136, 2096, 2340, 2308 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Rotating the square by 45 degrees (so that its vertices lie on the coordinate axes) results in sequence A303644 instead. LINKS Kirill Ustyantsev, Graphic illustration PROG (Python) import math for n in range (1, 100): .count=0 ..for x in range (-math.ceil(math.sqrt(2)*n), math.ceil(math.sqrt(2)*n)): ...for y in range (-math.ceil(math.sqrt(2)*n), math.ceil(math.sqrt(2)*n)): ....if (x*x+y*y>n*n and abs(x)+abs(y) n^2) && ((abs(x)+abs(y))^2 < 2*n^2))); \\ Michel Marcus, May 22 2018 CROSSREFS Cf. A302829, A303642, A303644. Sequence in context: A251643 A070710 A048759 * A298036 A119877 A307842 Adjacent sequences:  A303643 A303644 A303645 * A303647 A303648 A303649 KEYWORD nonn AUTHOR Kirill Ustyantsev, Apr 27 2018 STATUS approved

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Last modified September 22 12:19 EDT 2019. Contains 327307 sequences. (Running on oeis4.)