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A168626 Numbers n such that n and n+-1 have 3 or more distinct prime factors. 3
645, 741, 805, 987, 1035, 1065, 1105, 1221, 1275, 1309, 1310, 1463, 1495, 1581, 1749, 1885, 1886, 1925, 1989, 2014, 2015, 2109, 2135, 2211, 2255, 2261, 2289, 2295, 2331, 2355, 2365, 2379, 2409, 2465, 2485, 2541, 2584, 2585, 2665, 2666, 2667, 2679, 2685 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

MATHEMATICA

f[n_]:=Length[FactorInteger[n]]; lst={}; Do[If[f[n]>=3&&f[n-1]>=3&&f[n+1]>=3, AppendTo[lst, n]], {n, 7!}]; lst

Mean/@SequencePosition[Table[If[PrimeNu[n]>2, 1, 0], {n, 2700}], {1, 1, 1}] (* The program uses the SequencePosition function from Mathematica version 10 *) (* Harvey P. Dale, Jun 05 2016 *)

CROSSREFS

Cf. A140077

Sequence in context: A089295 A195808 A260838 * A216023 A100873 A227136

Adjacent sequences:  A168623 A168624 A168625 * A168627 A168628 A168629

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 01 2009

EXTENSIONS

Definition clarified by Harvey P. Dale, Jun 05 2016

STATUS

approved

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Last modified July 26 00:44 EDT 2017. Contains 289798 sequences.