|
|
A258775
|
|
Numbers n such that 1 + sigma(n)+ sigma(n)^2 is prime.
|
|
3
|
|
|
1, 2, 5, 6, 7, 8, 11, 13, 14, 15, 19, 23, 34, 37, 40, 45, 49, 53, 57, 58, 60, 61, 78, 79, 89, 92, 105, 106, 109, 123, 129, 132, 137, 138, 140, 141, 143, 148, 149, 154, 155, 156, 160, 161, 163, 165, 167, 182, 188, 191, 193, 195, 201, 208, 212, 213, 222, 226
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
MAPLE
|
select(isprime @ (t -> 1+t+t^2) @ numtheory:-sigma, [$1..1000]); # Robert Israel, Jun 09 2015
|
|
MATHEMATICA
|
Select[ Range[10000], PrimeQ[ 1 + DivisorSigma[1, #] + DivisorSigma[1, #]^2] & ]
Select[ Range[10000], PrimeQ[ Cyclotomic[3, DivisorSigma[1, #]]] &]
|
|
PROG
|
(PARI) for(n=1, 10^3, if(isprime(1+sigma(n)+sigma(n)^2), print1(n, ", "))) \\ Derek Orr, Jun 09 2015
(Magma) [n: n in [1..250] | IsPrime(1 + SumOfDivisors(n)+ SumOfDivisors(n)^2)]; // Vincenzo Librandi, Jun 10 2015
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|