OFFSET
1,1
COMMENTS
Subsequence of A067531. - Michel Marcus, Dec 22 2014
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
6 is composite and has 4 divisors (1, 2, 3, 6); 6 - 4 = 2, which is prime, so 6 is in the sequence.
15 is composite and has 4 divisors (1, 3, 5, 15); 15 - 4 = 11, which is prime, so 15 is in the sequence.
16 is composite and has 5 divisors (1, 2, 4, 8, 16); 16 - 5 = 11, which is prime, so 16 is in the sequence.
MATHEMATICA
Select[Range[500], CompositeQ[#] && PrimeQ[# - DivisorSigma[0, #]] &] (* Amiram Eldar, Jul 16 2019 *)
PROG
(Magma) [k:k in [1..500]|not IsPrime(k) and IsPrime(k-#Divisors(k))]; // Marius A. Burtea, Jul 16 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 16 2009, Nov 14 2009
EXTENSIONS
Extended by R. J. Mathar, May 19 2010
STATUS
approved