OFFSET
1,1
COMMENTS
These primes are not sorted nor unique. They are listed in the order found.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 19: sigma(3) + sigma(3)^2 - 1 = 4 + 16 - 1 = 19, which is prime.
a(5) = 239: sigma(8) + sigma(8)^2 - 1 = 15 + 225 - 1 = 239, which is prime.
MAPLE
MATHEMATICA
Select[Table[DivisorSigma[1, n] + DivisorSigma[1, n]^2 - 1, {n, 1, 10000}], PrimeQ]
PROG
(PARI) for(n=1, 100, k=sigma(n)+sigma (n)^2-1; if(isprime(k), print1(k, ", "))); \\ K. D. Bajpai, Jun 20 2015
(Magma) [k: n in [1..100] | IsPrime(k) where k is SumOfDivisors(n)+ SumOfDivisors(n)^2-1]; // K. D. Bajpai, Jun 20 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, Jun 20 2015
STATUS
approved