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A128284 a[n]= is the n-th smallest product of 3 odd primes m=p1*p2*p3, such that (d+m/d)/2 are all primes for each d dividing m. 4

%I

%S 105,165,273,345,357,385,777,897,1045,1173,1353,1653,1677,1705,2193,

%T 2233,2373,2905,3157,3237,3333,3417,3445,3553,3565,3945,4053,4585,

%U 4953,5665,5817,6097,6513,6693,7077,7833,8437,8565,8845,10153,11005,11433

%N a[n]= is the n-th smallest product of 3 odd primes m=p1*p2*p3, such that (d+m/d)/2 are all primes for each d dividing m.

%e 165=3.5.11 and (3.5.11+1)/2=83, (3+5.7)/2=19, (5+3.7)/2=13, (7+3.5)/2=11 are all primes and 165 is the 2nd smallest number of such form, so a[2]=165

%Y Cf. A128281, A005383, A128283, A128285, A128286.

%K nonn

%O 1,1

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

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Last modified April 5 16:53 EDT 2020. Contains 333245 sequences. (Running on oeis4.)