OFFSET
1,1
LINKS
Paolo P. Lava, Table of n, a(n) for n = 1..1000
EXAMPLE
83 is in the sequence because: it is prime, the sum of divisors (excluding 1 and 82) of 82 is 2 + 41 = 43, which is prime, and the sum of divisors (excluding 1 and 84) of 84 is 2 + 3 + 4 + 6 + 7 + 12 + 14 + 21 + 28 + 42 = 139, which is also prime.
MATHEMATICA
Select[Prime[Range[2, 900]], AllTrue[{Total[Most[Rest[Divisors[#-1]]]], Total[ Most[Rest[Divisors[#+1]]]]}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 29 2016 *)
PROG
(PARI) is(n)=isprime(n)&&isprime(sigma(n-1)-n)&&isprime(sigma(n+1)-n-2) \\ Charles R Greathouse IV, Feb 25 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Gerasimov Sergey, Feb 25 2013
EXTENSIONS
Extended and a(4) and a(6) inserted by Charles R Greathouse IV, Feb 25 2013
STATUS
approved