OFFSET
1,1
COMMENTS
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
EXAMPLE
6 is in sequence because sigma(6) - 1 = 12 - 1 = 11 (prime).
MAPLE
with(numtheory): A248792:=n->`if`(isprime(sigma(n)-1), n, NULL): seq(A248792(n), n=1..200); # Wesley Ivan Hurt, Jul 09 2015
MATHEMATICA
Select[Range[110], PrimeQ[DivisorSigma[1, #] - 1] &] (* Vincenzo Librandi, Nov 02 2014 *)
PROG
(Magma) [n: n in[1..1000] | IsPrime(SumOfDivisors(n) - 1)]
(PARI) for(n=1, 10^3, if(isprime(sigma(n)-1), print1(n, ", "))) \\ Derek Orr, Nov 01 2014
CROSSREFS
Cf. A065512 (numbers n such that sigma(n) + 1 is prime).
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Nov 01 2014
STATUS
approved