A187554 Odd nonprimes n such that n+d+1 is prime for all divisors d of n.

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

Offset: 1

Author

Juri-Stepan Gerasimov, Mar 26 2011

Keywords

• nonn

Examples

			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.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A120776, A120806, A120811.

Programs

Mathematica

Select[Range[1,29001,2],!PrimeQ[#]&&AllTrue[#+Divisors[#]+1,PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 21 2016 *)

Formula

A120776(a(n+1)) = A120806(a(n+1)).