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 A047824 Becomes prime after exactly 5 iterations of f(x) = sum of prime factors of x. 0

%I

%S 134,177,262,268,398,422,466,524,531,536,573,614,669,706,742,753,796,

%T 817,818,844,849,898,915,921,932,933,934,974,1006,1048,1072,1149,1165,

%U 1202,1222,1227,1228,1238,1239,1243,1294,1322,1347,1354,1385,1393,1398

%N Becomes prime after exactly 5 iterations of f(x) = sum of prime factors of x.

%C f(x) = sum of prime factors without multiplicity, so that f(1500) = 2+3+5 = 10.

%t p5iQ[n_]:=PrimeQ[NestList[Total[Transpose[FactorInteger[#]][[1]]]&,n,5]] == {False,False,False,False,False,True}; Select[Range[2000],p5iQ] (* _Harvey P. Dale_, May 21 2015 *)

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified November 27 14:41 EST 2022. Contains 358405 sequences. (Running on oeis4.)