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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
1365, 4305, 10465, 11685, 15873, 27105, 31845, 35245, 50065, 54033, 58765, 74965, 84513, 91977, 95557, 95613, 96033, 104377, 113997, 114405, 117957, 118105, 126357, 127605, 136437, 170905, 197985, 209605, 215373, 226185, 248385, 277797 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

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,

(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

CROSSREFS

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

Sequence in context: A043578 A004970 A234501 * A069310 A096117 A140936

Adjacent sequences:  A128282 A128283 A128284 * A128286 A128287 A128288

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified April 6 21:24 EDT 2020. Contains 333286 sequences. (Running on oeis4.)