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Primes of the form (p*q - 2)/5 where p and q are successive primes.
1

%I #17 May 26 2024 08:29:37

%S 229,1153,14149,15013,189733,214657,253573,350593,514561,522289,

%T 725041,853669,1304581,1453681,2027569,2183281,2212453,2469637,

%U 3238513,4166017,4331941,4467013,5234689,5510371,5992933,6102913,8100097,8130673

%N Primes of the form (p*q - 2)/5 where p and q are successive primes.

%C These numbers times 5 are semiprimes.

%H Amiram Eldar, <a href="/A124684/b124684.txt">Table of n, a(n) for n = 1..10000</a>

%e 31*37 = 1147, 1147-2 = 1145, 1145/5 = 229 is a term.

%t Select[(Times @@@ Partition[Prime[Range[1000]], 2, 1] - 2) / 5, PrimeQ] (* _Amiram Eldar_, May 26 2024 *)

%o (PARI) g(n,p=5) = { for(x=1,n, y=prime(x)*prime(x+1)-2; if(y%p==0,if(isprime(y/p), print1(y/p, ", ")))) }

%Y Cf. A123921.

%K easy,nonn

%O 1,1

%A _Cino Hilliard_, Dec 27 2006