|
|
A187554
|
|
Odd nonprimes n such that n+d+1 is prime for all divisors d of n.
|
|
1
|
|
|
1, 9, 35, 39, 65, 125, 749, 755, 905, 935, 989, 1469, 1829, 1859, 2519, 3161, 4269, 4859, 5165, 5699, 6005, 7319, 8309, 8759, 9155, 9869, 11129, 12819, 12851, 14141, 14279, 15539, 15899, 18689, 19859, 20019, 25115, 25535, 26679, 28049
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
a(6) = 125 with divisors (1, 5, 25, 125) and the set of all n+d+1 is (127, 131, 151, 251) and these are all prime.
|
|
MATHEMATICA
|
Select[Range[1, 29001, 2], !PrimeQ[#]&&AllTrue[#+Divisors[#]+1, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 21 2016 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|