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%I #16 Oct 09 2023 09:24:51
%S 3,0,1,2,4,8,12,32,36,40,24,48,160,396,2268,704,312,72,336,216,936,
%T 144,624,1056,1760,360,2560,384,288,1320,3696,240,768,9000,432,7128,
%U 4200,480,576,1296,1200,15936,3312,3072,3240,864,3120,7344,3888,720,1680
%N Smallest k such that phi(x) = k has exactly n solutions.
%C Carmichael conjectured that no term exists for n=1.
%D M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 840.
%H M. Abramowitz and I. A. Stegun, eds., <a href="http://www.convertit.com/Go/ConvertIt/Reference/AMS55.ASP">Handbook of Mathematical Functions</a>, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
%H Max Alekseyev, <a href="http://home.gwu.edu/~maxal/gpscripts/">PARI scripts for various problems</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CarmichaelsTotientFunctionConjecture.html">Carmichael's Totient Function conjecture</a>
%o (PARI) a(n) = if (n==1, 0, my(k=1); while (#invphi(k) != n, k++); k); \\ using invphi in PARI scripts link; _Michel Marcus_, Oct 09 2023
%Y Cf. A000010. Essentially same as A007374, which is the main entry for this sequence.
%K nonn,easy
%O 0,1
%A _Eric W. Weisstein_
%E Link fixed by _Charles R Greathouse IV_, Oct 06 2009
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