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 A073257 Smallest n such that gcd(c(x),x) = gcd(A002808(x),x) = A064814(x) = n. 1

%I

%S 1,2,12,20,5,6,7,64,234,50,55,24,26,28,30,32,629,1008,209,220,231,

%T 1012,506,168,425,182,189,2716,2204,1080,93,96,99,2176,105,4428,1369,

%U 5586,1755,1800,6109,2478,2279,3916,5760,644,4606,1920,1960,10250,2040,2444

%N Smallest n such that gcd(c(x),x) = gcd(A002808(x),x) = A064814(x) = n.

%F a(n) = min{x: gcd(c(x), x)=n}, where c(x) is the x-th composite number.

%e 50th composite is 70, gcd(50,70)=10 appears first here, a(10)=50.

%t f[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] t=Table[0, {100}]; Do[s=GCD[f[n], n]; If[s<101&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t

%Y Cf. A064814, A002808, A073258.

%K nonn

%O 1,2

%A _Labos Elemer_, Jul 22 2002

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Last modified January 27 12:01 EST 2020. Contains 331295 sequences. (Running on oeis4.)