login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A065512 Numbers n such that sigma(n) + 1 is prime. 8
1, 3, 5, 6, 10, 11, 12, 17, 20, 22, 24, 26, 27, 29, 30, 38, 41, 42, 45, 46, 51, 55, 59, 62, 68, 69, 71, 77, 82, 85, 88, 91, 99, 101, 104, 105, 106, 107, 108, 114, 116, 118, 125, 126, 132, 135, 136, 137, 140, 141, 145, 146, 147, 149, 150, 155, 158, 160, 161 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
sigma(10) + 1 = 18 + 1 = 19 (prime). sigma(24) + 1 = 60 + 1 = 61 (prime).
MAPLE
select(isprime @ (1+numtheory:-sigma), [$1..1000]); # Robert Israel, May 29 2015
MATHEMATICA
Select[ Range[170], PrimeQ[ DivisorSigma[1, # ] + 1] & ]
PROG
(PARI) { n=0; for (m=1, 10^9, if (isprime(sigma(m) + 1), write("b065512.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Oct 20 2009
(Magma) [n: n in [1..200] | IsPrime(1+SumOfDivisors(n))]; // Vincenzo Librandi, May 30 2015
CROSSREFS
Sequence in context: A232531 A182637 A331915 * A066147 A175304 A140951
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Nov 26 2001
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)