A128285 Numbers of the form m = p1 * p2 * p3 * p4 where for each d|m we have (d+m/d)/2 prime and p1 < p2 < p3 < p4 each prime.

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

Offset

1,1

Links

David A. Corneth, Table of n, a(n) for n = 1..3114

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 1365 is in the sequence.

Crossrefs

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

Subsequence of A046390.

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

Extensions

New name from David A. Corneth, Jan 09 2021

Status

approved