A168630 Numbers n such that n, n+1, and the sum of those two numbers each have 4 or more distinct prime factors.

46189, 50634, 69597, 76797, 90117, 97954, 108205, 115804, 127347, 138957, 144627, 159340, 164020, 166022, 166497, 166705, 167205, 167485, 173194, 174454, 181670, 186294, 190014, 193154, 198789, 211029, 212134, 214225, 217217, 221815, 222547, 224146

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Dec 01 2009

Keywords

• nonn

Examples

			FactorInteger[46189]=11*13*17*19, FactorInteger[46190]=2*5*31*149, FactorInteger[46189+46190]=3*7*53*83,..
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A140077, A140078, A168626, A168628, A168629

Programs

Maple

g:= proc(n) option remember; nops(numtheory:-factorset(n))>=4 end proc:
filter:= n -> g(n) and g(n+1) and g(2*n+1):
select(filter, [$1..300000]); # Robert Israel, May 09 2018

Mathematica

f[n_]:=Length[FactorInteger[n]]; lst={};Do[If[f[n]>=4&&f[n+1]>=4&&f[n+n+1]>=4,AppendTo[lst,n]],{n,9!}];lst
Select[Range[225000],Min[Thread[PrimeNu[{#,#+1,2#+1}]]]>3&](* Harvey P. Dale, Nov 11 2017 *)

Extensions

Definition modified and terms extended by Harvey P. Dale, Nov 11 2017