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
Keywords
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
Programs
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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
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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