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A078762
Numbers n such that n + sigma(n) is prime.
6
1, 2, 3, 4, 5, 8, 11, 16, 21, 23, 27, 29, 35, 36, 41, 53, 55, 57, 63, 64, 65, 75, 77, 83, 85, 89, 98, 100, 111, 113, 119, 125, 128, 131, 133, 143, 144, 155, 161, 171, 173, 179, 183, 189, 191, 203, 205, 209, 215, 233, 235, 237, 239, 242, 243, 245, 251, 253, 259, 275
OFFSET
1,2
COMMENTS
Union of A005384 (Sophie Germain primes) and A249486. - Jaroslav Krizek, Nov 13 2014
LINKS
MAPLE
select(t -> isprime(t+numtheory:-sigma(t)), [$1..1000]); # Robert Israel, May 01 2018
MATHEMATICA
Select[Range[10^3], PrimeQ[ # + DivisorSigma[1, # ]] &]
PROG
(PARI) for(n=1, 1000, if(isprime(sigma(n)+n), print1(n, ", "))) \\ Derek Orr, Nov 13 2014
CROSSREFS
Sequence in context: A271488 A333347 A302592 * A103262 A135318 A374782
KEYWORD
nonn,easy
AUTHOR
Joseph L. Pe, Jan 08 2003
STATUS
approved