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A147853 Least prime p such that there is a prime q with (p+q)/2=A002110(n), the n-th primorial. 1


%S 5,7,11,17,19,19,29,37,37,37,73,47,59,71,97,79,79,101,97,137,227,137,

%T 109,127,151,127,151,151,179,227,431,139,211,223,337,181,251,257,313,

%U 227,257,227,263,491,307,241,409,263,277

%N Least prime p such that there is a prime q with (p+q)/2=A002110(n), the n-th primorial.

%C If q>10^22 then q is a probable prime. - _Pierre CAMI_, Jan 07 2014

%H Pierre CAMI, <a href="/A147853/b147853.txt">Table of n, a(n) for n = 2..1376</a>

%e For primorial=30, (p,q)=(7,53) as 7+53=2*30.

%o (PARI) ospp(N)= { i=4; while(1, Q=2*N-prime(i); if( ispseudoprime(2*N-prime(i)),print(N,", ",prime(i) );return(1) ); i++ ); \end WHILE }

%Y Cf. A002110, A147517

%K easy,nonn

%O 2,1

%A _Bill McEachen_, Nov 15 2008

%E Improved description from _T. D. Noe_

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Last modified December 10 20:38 EST 2019. Contains 329909 sequences. (Running on oeis4.)