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A128278 an=n-th smallest integer m=p1*p2*p3, product of 3 odd primes such that d+2m/d are all primes for d dividing 2m. 2

%I

%S 105,165,231,935,2109,2795,3021,3819,6981,7205,11285,12341,13101,

%T 16419,17549,19839,21749,21995,26391,31229,31269,46631,62651,63645,

%U 65391,76155,77585,100955,110811,113555,118031,136451,148359,150245,154679

%N an=n-th smallest integer m=p1*p2*p3, product of 3 odd primes such that d+2m/d are all primes for d dividing 2m.

%e E.g. 105=3.5.7, 2.3.5.7+1=211, 2+3.5.7=107, 3+2.5.7=73, 5+2.3.7=47, 7+2.3.5=37, 2.3+5.7=41, 2.5+3.7=31, 2.7+3.5=29 are all primes and 3.5.7 is the smallest such number, so a(1)=105.

%Y Cf. A128276, A128277, A128279, A045536.

%K nonn

%O 1,1

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

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Last modified November 17 00:08 EST 2019. Contains 329209 sequences. (Running on oeis4.)