OFFSET
1,1
COMMENTS
A simpler version of A179945, added at the request of the editor-in-chief.
MAPLE
q:= n-> (t-> andmap(isprime, [t-n-1, t-2*n-1]))(numtheory[sigma](n)):
select(q, [$1..1500])[]; # Alois P. Heinz, Mar 21 2023
PROG
(PARI) is(n)=my(s=sigma(n)); isprime(s-n-1) && isprime(s-n-n-1) \\ Charles R Greathouse IV, Feb 19 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Aug 18 2010
EXTENSIONS
Edited by N. J. A. Sloane, Aug 28 2010
STATUS
approved