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A128277 a(n) is the n-th smallest integer m which is the product of 4 odd primes m=p1*p2*p3*p4 such that d+2*m/d are all primes for each d dividing 2*m. 3

%I

%S 93081,449985,1523705,301921991,899343761,1581262341,7290929465,

%T 12102153569,25404516309,27482957831,38661868781,49656488021,

%U 240305617889,305000299185,341656377581,377737353491

%N a(n) is the n-th smallest integer m which is the product of 4 odd primes m=p1*p2*p3*p4 such that d+2*m/d are all primes for each d dividing 2*m.

%C 1. a(6)>2*10^9 2. (C. Pomerance) The prime k-tuple conjecture implies the sequence is infinite.

%C a(17) > 4*10^11. [From _Donovan Johnson_, Sep 06 2010]

%e 93081=3*19*23*71 and 2*93081+1, 2+3*19*23*71, 3+2*19*23*71, 19+2*3*23*71, 71+2*3*19*23, 2*3+19*23*71, 2*19+3*23*71, 2*23+3*19*23*71, 2*71+3*19*23, 3*19+2*23*71, 3*23+2*19*71, 3*71+2*19*23, 19*23+2*3*71, 19*71+2*3*23, 23*71+2*3*19 are all primes and 93081 is smallest such integer, so a(1)=93081

%Y Cf. A128276.

%K hard,more,nonn

%O 1,1

%A Kok Seng Chua (chuakokseng(AT)hotmail.com), Feb 23 2007

%E Changed every occurrence of 93801 to 93081 -- _T. D. Noe_, Aug 05 2010

%E Added missing term 899343761 and a(7)-a(16) from _Donovan Johnson_, Sep 06 2010

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Last modified March 21 20:15 EDT 2019. Contains 321382 sequences. (Running on oeis4.)