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A128285 a[n]= is the n-th smallest product of 4 odd primes m=p1*p2*p3*p4, such that (d+m/d)/2 are all primes for each d dividing m. 4

%I

%S 1365,4305,10465,11685,15873,27105,31845,35245,50065,54033,58765,

%T 74965,84513,91977,95557,95613,96033,104377,113997,114405,117957,

%U 118105,126357,127605,136437,170905,197985,209605,215373,226185,248385,277797

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

%e 1365=3.5.7.13 and (3.5.7.13+1)/2, (3+5.7.13)/2, (5+3.7.13)/2, (7+3.5.13)/2,

%e (13+3.5.7)/2, (3.5+7.13)/2, (3.7+5.13)/2, (3.13+5.7)/2 are all primes and 1365 is the smallest such integer which is the product of 4 primes, so a[1]=1365

%Y Cf. A128281, A005383, A128283, A128284, A128286.

%K nonn

%O 1,1

%A Kok Seng Chua (chuakokseng(AT)hotmail.com), Mar 05 2007

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Last modified May 28 17:37 EDT 2020. Contains 334684 sequences. (Running on oeis4.)