A168628 - OEIS

A168628

Numbers n such that n and n+-1 have 4 distinct prime factors.

37961, 44485, 45695, 50141, 51429, 55131, 55385, 61335, 63365, 64295, 67165, 68265, 68475, 70005, 70091, 71709, 72709, 76153, 80445, 81549, 81719, 82041, 84435, 85491, 86241, 90364, 95381, 97383, 98021, 99085, 99385, 99429, 99789, 100165, 100491, 100595

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..36.

MATHEMATICA

f[n_]:=Length[FactorInteger[n]]; lst={}; Do[If[f[n]>=4&&f[n-1]>=4&&f[n+1]>=4, AppendTo[lst, n]], {n, 9!}]; lst

SequencePosition[PrimeNu[Range[110000]], {4, 4, 4}][[All, 1]]+1 (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 27 2018 *)

PROG

(PARI) is(n)=omega(n)==4 && omega(n+1)==4 && omega(n-1)==4 \\ Charles R Greathouse IV, Jan 25 2025

CROSSREFS

Subsequence of A140078.