|
%I #9 Oct 19 2023 18:17:27
%S 271,593,701,751,919,1169,1241,1639,1649,1673,1711,1751,2071,2311,
%T 2393,2549,2551,2609,2729,2861,2863,2897,2899,3185,3331,3569,3631,
%U 3823,3849,3851,3943,3977,4231,4265,4649,4663,5071,5081,5237,5239,5391,5551,5561,5585,5741
%N Numbers k such that k-+1 are divisible by exactly 5 primes, counted with multiplicity.
%H Jinyuan Wang, <a href="/A157485/b157485.txt">Table of n, a(n) for n = 1..5000</a>
%t q=5;lst={};Do[If[Plus@@Last/@FactorInteger[n-1]==q&&Plus@@Last/@FactorInteger[n+1]==q,AppendTo[lst,n]],{n,7!}];lst
%t Select[Range[6000],PrimeOmega[#+{1,-1}]=={5,5}&] (* _Harvey P. Dale_, Jun 05 2021 *)
%t Mean/@SequencePosition[PrimeOmega[Range[6000]],{5,_,5}] (* _Harvey P. Dale_, Oct 19 2023 *)
%o (PARI) is(k) = bigomega(k-1)==5 && bigomega(k+1)==5; \\ _Jinyuan Wang_, Mar 22 2020
%Y Cf. A014612, A124936, A157483, A157484.
%K nonn
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Mar 01 2009
%E More terms from _Jinyuan Wang_, Mar 22 2020
|
