login
A328736
Numbers k such that at least one of sopfr(k-1) and sopfr(k+1) is greater than or equal to 2*sopfr(k).
2
16, 18, 20, 24, 28, 30, 32, 36, 40, 42, 44, 45, 48, 52, 54, 60, 63, 66, 68, 70, 72, 75, 78, 80, 81, 84, 85, 88, 90, 95, 96, 98, 100, 102, 104, 105, 108, 110, 112, 114, 117, 119, 121, 125, 126, 128, 130, 132, 133, 135, 136, 138, 140, 143, 144, 145
OFFSET
1,1
COMMENTS
k-1 or k+1 or both have sums of prime factors at least twice the sum of prime factors of k.
MATHEMATICA
sop[n_] := If[n<2, 0, Total[Times @@@ FactorInteger@ n]]; Select[ Range[2, 150], (s = 2 sop[#]; sop[#+1] >= s || sop[#-1] >= s) &] (* Giovanni Resta, Oct 27 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Bilinski, Oct 26 2019
STATUS
approved