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Least number k>0 such that x' = k has n solutions, where x' is the arithmetic derivative (A003415) of x.
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%I #18 Oct 08 2012 14:57:24

%S 2,4,10,16,24,54,48,60,84,90,114,144,150,120,168,234,216,252,288,210,

%T 354,240,432,360,330,552,456,390,462,480,546,420,510,600,672,792,756,

%U 714,798,690,720,630,1116,1026,930,780,870,960,900,924,1134,1296,840

%N Least number k>0 such that x' = k has n solutions, where x' is the arithmetic derivative (A003415) of x.

%C It appears that all terms are even. See A189559 for k restricted to prime numbers and A189560 restricted to odd numbers.

%D See A003415.

%H T. D. Noe and Donovan Johnson, <a href="/A189558/b189558.txt">Table of n, a(n) for n = 0..5000</a> (terms up to a(665) from T. D. Noe)

%F a(n) is the least k>0 such that A099302(k) = n.

%Y See A003415, A099302, A189559, A189560.

%K nonn

%O 0,1

%A _T. D. Noe_, Apr 24 2011