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 A214628 Intersections of radii with the cycloid. 0
 2, 2, 2, 2, 4, 4, 4, 6, 6, 6, 8, 8, 8, 8, 10, 10, 10, 12, 12, 12, 14, 14, 14, 16, 16, 16, 18, 18, 18, 20, 20, 20, 22, 22, 22, 22, 24, 24, 24, 26, 26, 26, 28, 28, 28, 30, 30, 30, 32, 32, 32, 34, 34, 34, 36, 36, 36, 36, 38, 38, 38, 40, 40, 40 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Number of times the line y=x/n intersects the cycloid specified by x=t-sin(t), y=1-cos(t) or, by symmetry, number of times the line y=n*x intersects the cycloid specified by x=1-cos(t), y=t-sin(t). It is equal to twice the number of arches that are intersected by the lines (2 intersection points by arch). To find this sequence one can look for the slopes of the tangents to the n-th arch when these tangents pass through the origin (see pari script). If one consider the indices where a(n) change value, one gets: 1, 4, 7, 10, 14, 17, 20, 23, 26, ... that may well be A062389, as this is the slope of the line joining the origin to the summit of the n-th arch. Will this be true for all n? - Michel Marcus, Aug 29 2013 LINKS EXAMPLE For n=1,...4 a(n)=2; for n=5,...7 a(n)=4. PROG (PARI) slop(n) = {ang = 2*n*Pi; val = solve(x=ang + Pi/100, ang + Pi, 2 - 2*cos(x) - x*sin(x)); vinvn = floor((1 - cos(val))/sin(val)); } lista(nn) = {nbc = 0; nbi = 1; for (i=1, nn, nnbc = slop(i); for (j = 1, nnbc - nbc, print1(2*nbi, ", ")); nbi++; nbc = nnbc; ); } \\ Michel Marcus, Aug 29 2013 CROSSREFS Sequence in context: A035398 A104409 A274144 * A032576 A276420 A239494 Adjacent sequences:  A214625 A214626 A214627 * A214629 A214630 A214631 KEYWORD nonn AUTHOR Gordon Roesler, Jul 23 2012 EXTENSIONS More terms from Michel Marcus, Aug 29 2013 STATUS approved

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Last modified July 13 05:18 EDT 2020. Contains 335673 sequences. (Running on oeis4.)