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

Author

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

Keywords

• nonn

Examples

			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.
		

Links

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

Crossrefs

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

Subsequence of A046390.

Extensions

New name from David A. Corneth, Jan 09 2021