OFFSET
1,1
COMMENTS
f(x) = sum of prime factors without multiplicity, so that f(1500) = 2+3+5 = 10.
MATHEMATICA
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 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved