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Consider sequence of fractions A066657/A066658 produced by ratios of terms in A066720; let m = smallest integer such that all fractions 1/n, 2/n, ..., (n-1)/n have appeared when we reach A066720(m) = k; sequence gives values of k; set a(n) = -1 if some fraction i/n never appears.
3

%I #14 Nov 19 2017 21:58:41

%S 1,2,3,2436,520,60,308,2436,15867,61800,8096,55620,77077,20216,51675,

%T 2296992,21607,15867,185820,481680,140805,226644,145866,1568928,

%U 1076000,187772,5596587,1831956,715778,3540060,836535,2296992,3088008,1129514,7096775,1995048,2018646,3159168,13019136,15293320,6936667,11250624,6877463,20475136,3380040,3986360,1052424,17566608,5152350,1076000,3824694,8897564,2987239,17600004,24056230,89537336,23397531,2791424,5393780,19344660,5306268,8679008,126415359,30486400,29303235

%N Consider sequence of fractions A066657/A066658 produced by ratios of terms in A066720; let m = smallest integer such that all fractions 1/n, 2/n, ..., (n-1)/n have appeared when we reach A066720(m) = k; sequence gives values of k; set a(n) = -1 if some fraction i/n never appears.

%e 3/4 does not occur until we reach A066720(401) = 2436 and then we see A066720(320)/A066720(401) = 1827/2436 = 3/4. Therefore a(4) = 2436.

%Y Cf. A066720, A066657, A066658. A066849 gives values of m.

%K nonn,nice

%O 1,2

%A _N. J. A. Sloane_, Jan 21 2002

%E Corrected by _John W. Layman_, Feb 05 2002

%E Greatly extended by _David Applegate_, Feb 13 2002