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%I #9 Oct 21 2014 10:14:53
%S 134,177,213,262,309,334,339,398,445,469,505,514,534,606,670,723,742,
%T 753,758,763,788,793,802,804,817,818,849,865,913,914,915,926,961,976,
%U 998,1011,1016,1038,1052,1060,1090,1098,1101,1115,1143,1154,1165,1195
%N Becomes prime or 4 after exactly 6 iterations of f(x) = sum of prime factors of x.
%C f(x) = sum of prime factors with multiplicity, so that f(1500) = 2+2+3+5+5+5 = 22.
%H Harvey P. Dale, <a href="/A048128/b048128.txt">Table of n, a(n) for n = 1..3500</a>
%t nxt[n_]:=Total[Flatten[Table[#[[1]],{#[[2]]}]&/@FactorInteger[n]]]; sixiQ[ n_]:=Module[{c=NestList[nxt,n,6]},PrimeQ[c]=={False,False,False,False,False,False,True} || FirstPosition[ c,4,1] == {7}]; Select[ Range[ 1200],sixiQ] (* _Harvey P. Dale_, Oct 21 2014 *)
%K nonn
%O 1,1
%A _David W. Wilson_
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