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%I #18 Sep 08 2022 08:46:15
%S 53,89,449,683,1259,4283,6803,11789,12781,13553,16561,18593,18899,
%T 20287,29303,35099,36217,37619,52163,54181,64763,65213,67103,103769,
%U 115831,116009,125551,126541,147997,154043,155161,155609,166013,173699,181943,188911,190261,196613
%N Primes p such that p+-2 and p+-4 are semiprimes.
%H Robert Israel, <a href="/A266845/b266845.txt">Table of n, a(n) for n = 1..2500</a>
%e a(1)=53 because 53 - 2 = 51 = 3*17, 53 + 2 = 55 = 5*11.
%p filter:= proc(n) andmap(t -> numtheory:-bigomega(t)=2, [n-4,n-2,n+2,n+4]) end proc:
%p select(filter, [seq(ithprime(i),i=1..20000)]); # _Robert Israel_, Aug 11 2019
%t Select[Prime@ Range@ 18000, AllTrue[# + {-4, -2, 2, 4}, PrimeOmega@ # == 2 &] &] (* _Michael De Vlieger_, Jan 09 2016, Version 10 *)
%o (PARI) lista(nn) = {forprime(p=5, nn, if (bigomega(p-4)==2 && bigomega(p+4)==2 && bigomega(p-2)==2 && bigomega(p+2)==2, print1(p, ", ")); ); } \\ _Michel Marcus_, Jan 10 2016
%o (Magma) IsSemiprime:=func< p | &+[ k[2]: k in Factorization(p)] eq 2 >; [p: p in PrimesInInterval(3,2*10^5)| IsSemiprime(p+2) and IsSemiprime(p+4)and IsSemiprime(p-2) and IsSemiprime(p-4)]; // _Vincenzo Librandi_, Jan 10 2016
%Y Subsequence of A063643.
%K nonn
%O 1,1
%A _Zak Seidov_, Jan 04 2016
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