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 A047977 Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p2. 2

%I #9 Jul 19 2016 10:23:45

%S 7,13,43,73,601,643,883,2131,2383,2689,3559,3583,4549,6133,7549,8011,

%T 9043,13399,13933,15973,17599,19141,21493,26251,26263,34513,38671,

%U 39229,39343,48313,49741,52543,53089,53593,55051,55663,56101

%N Let (p1,p2), (p3,p4) be pairs of twin primes with p1*p2=p3+p4-1; sequence gives values of p2.

%H Charles R Greathouse IV, <a href="/A047977/b047977.txt">Table of n, a(n) for n = 1..10000</a>

%e E.g. 5*7=17+19-1,11*13=71+73-1.

%o (PARI) list(lim)=my(v=List(),p=3,r); forprime(q=5,lim, if(q-p==2 && isprime(r=p*q\2) && isprime(r+2), listput(v,q)); p=q); Vec(v) \\ _Charles R Greathouse IV_, Sep 29 2015

%o (PARI) is(n)=isprime(n) && isprime(n-2) && isprime(n*(n-2)\2) && isprime(n*(n-2)\2+2) \\ _Charles R Greathouse IV_, Sep 29 2015

%Y Cf. A047976-A047979.

%K nonn

%O 1,1

%A _Naohiro Nomoto_

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Last modified August 4 23:59 EDT 2024. Contains 374934 sequences. (Running on oeis4.)