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.

105, 165, 231, 935, 2109, 2795, 3021, 3819, 6981, 7205, 11285, 12341, 13101, 16419, 17549, 19839, 21749, 21995, 26391, 31229, 31269, 46631, 62651, 63645, 65391, 76155, 77585, 100955, 110811, 113555, 118031, 136451, 148359, 150245, 154679

Offset

1,1

Links

Table of n, a(n) for n=1..35.

Example

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.

Crossrefs

Cf. A128276, A128277, A128279, A045536.

Sequence in context: A256673 A308779 A046405 * A234103 A128284 A161962

Adjacent sequences: A128275 A128276 A128277 * A128279 A128280 A128281

Keyword

nonn

Author

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

Status

approved