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A006073
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Numbers k such that k, k+1 and k+2 all have the same number of distinct prime divisors.
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20
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2, 3, 7, 20, 33, 34, 38, 44, 50, 54, 55, 56, 74, 75, 85, 86, 91, 92, 93, 94, 98, 115, 116, 117, 122, 133, 134, 141, 142, 143, 144, 145, 146, 158, 159, 160, 175, 176, 183, 187, 200, 201, 205, 206, 207, 212, 213, 214, 215, 216, 217, 224, 235, 247
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OFFSET
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1,1
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COMMENTS
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Distinct prime divisors means that the prime divisors are counted without multiplicity. - Harvey P. Dale, Apr 19 2011
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LINKS
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FORMULA
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MATHEMATICA
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pdQ[n_]:=PrimeNu[n]==PrimeNu[n+1]==PrimeNu[n+2]; Select[Range[250], pdQ] (* Harvey P. Dale, Apr 19 2011 *)
Take[Transpose[Flatten[Select[Partition[{#, PrimeNu[#]}&/@Range[250000], 3, 1], #[[1, 2]]==#[[2, 2]]==#[[3, 2]]&], 1]][[1]], {1, -1, 3}] (* Harvey P. Dale, Dec 09 2011 *)
Flatten[Position[Partition[PrimeNu[Range[250]], 3, 1], _?(#[[1]]==#[[2]]== #[[3]]&), {1}, Heads->False]] (* Harvey P. Dale, Oct 30 2013 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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