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A171130 Primes p such that sum of divisors of p+2 is prime. 3
2, 7, 23, 727, 2399, 5039, 7919, 17159, 28559, 29927, 85847, 458327, 552047, 579119, 707279, 1190279, 3418799, 3728759, 4532639, 5166527, 5331479, 7447439, 10374839, 24137567, 25877567, 28398239, 30260999, 43546799, 47458319, 52258439, 56957207, 62425799 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

Divisors[2+2]={1,2,4}->7, Divisors[7+2]={1,3,9}->13, Divisors[23+2]={1,5,25}->31, Divisors[727+2]={1,3,9,27,81,243,729}->1093,..

MAPLE

with(numtheory): A171130:=n->`if`(isprime(n) and isprime(sigma(n+2)), n, NULL): seq(A171130(n), n=1..10^5); # Wesley Ivan Hurt, Sep 30 2014

MATHEMATICA

f[n_]:=Plus@@Divisors[n]; lst={}; Do[p=Prime[n]; If[PrimeQ[f[p+2]], AppendTo[lst, p]], {n, 10!}]; lst

Select[Prime[Range[700000]], PrimeQ[DivisorSigma[1, #+2]]&] (* Harvey P. Dale, Jun 23 2011 *)

PROG

(PARI) lista(nn) = forprime(p=2, nn, if (isprime(sigma(p+2)), print1(p, ", "))); \\ Michel Marcus, Sep 30 2014

CROSSREFS

Sequence in context: A032264 A139522 A163158 * A112089 A075062 A022497

Adjacent sequences:  A171127 A171128 A171129 * A171131 A171132 A171133

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 04 2009

EXTENSIONS

More terms from Michel Marcus, Sep 30 2014

STATUS

approved

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Last modified October 31 12:07 EDT 2014. Contains 248864 sequences.