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A321504 Numbers n such that n and n+1 each have at least 4 distinct prime factors. 7
7314, 8294, 8645, 9009, 10659, 11570, 11780, 11934, 13299, 13629, 13845, 14420, 15105, 15554, 16554, 16835, 17204, 17390, 17654, 17765, 18095, 18290, 18444, 18920, 19005, 19019, 19095, 19227, 20349, 20405, 20769, 21164, 21489, 21735, 22010, 22154, 22659, 23001, 23114, 23484, 23529, 23540, 23919, 24395 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Equals A140078 up to a(123) but a({124, 214, 219, 276, 321, 415, ...}) = {

38570, 51414, 51765, 58695, 62985, 71070, ...} are not in A140078, see A321494.

LINKS

M. F. Hasler, Table of n, a(n) for n = 1..10000

MATHEMATICA

SequencePosition[Table[If[PrimeNu[n]>3, 1, 0], {n, 25000}], {1, 1}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 29 2019 *)

PROG

(PARI) is(n)=omega(n)>=4&&omega(n+1)>=4

CROSSREFS

Cf. A140078, A321494.

Cf. A321505, A321506 (variant for k=5 & k=6 prime factors).

Sequence in context: A253939 A116248 A140078 * A318896 A328786 A295004

Adjacent sequences:  A321501 A321502 A321503 * A321505 A321506 A321507

KEYWORD

nonn

AUTHOR

M. F. Hasler, Nov 12 2018

STATUS

approved

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Last modified April 9 19:36 EDT 2020. Contains 333362 sequences. (Running on oeis4.)