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A140077 Numbers n such that n and n+1 have 3 distinct prime factors. 11
230, 285, 429, 434, 455, 494, 560, 594, 609, 615, 644, 645, 650, 665, 740, 741, 759, 804, 805, 819, 825, 854, 860, 884, 902, 935, 945, 969, 986, 987, 1001, 1014, 1022, 1034, 1035, 1044, 1064, 1065, 1070, 1085, 1104, 1105, 1130, 1196, 1209, 1220, 1221 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Goldston, Graham, Pintz, & Yildirim prove that this sequence is infinite. - Charles R Greathouse IV, Sep 14 2015

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..10000

D. A. Goldston, S. W. Graham, J. Pintz, C. Y. Yildirim, Small gaps between almost primes, the parity problem and some conjectures of Erdos on consecutive integers.

MATHEMATICA

a = {}; Do[If[Length[FactorInteger[n]] == 3 && Length[FactorInteger[n + 1]] == 3, AppendTo[a, n]], {n, 1, 100000}]; a (*Artur Jasinski*)

SequencePosition[PrimeNu[Range[1250]], {3, 3}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Feb 27 2017 *)

PROG

(PARI) is(n)=omega(n)==3&&omega(n+1)==3 \\ Charles R Greathouse IV, Sep 14 2015

CROSSREFS

Cf. A074851, A140078, A140079 .

Sequence in context: A177826 A122269 A171666 * A215217 A211711 A211716

Adjacent sequences:  A140074 A140075 A140076 * A140078 A140079 A140080

KEYWORD

nonn

AUTHOR

Artur Jasinski, May 07 2008

STATUS

approved

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Last modified June 29 03:09 EDT 2017. Contains 288858 sequences.