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A322842 Primes p such that both p+2 and p-2 are neither prime nor semiprime. 1
173, 277, 457, 607, 727, 929, 1087, 1129, 1181, 1223, 1237, 1307, 1423, 1433, 1447, 1493, 1523, 1549, 1597, 1613, 1627, 1811, 1861, 1973, 2011, 2063, 2137, 2297, 2347, 2377, 2399, 2423, 2677, 2693, 2753, 2767, 2797, 2819, 2851, 2917, 3023, 3313, 3323, 3449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also: Primes p such that both p+2 and p-2 have at least three prime divisors. - David A. Corneth, Dec 28 2018

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

MAPLE

q:= n-> numtheory[bigomega](n)>2:

a:= proc(n) option remember; local p;

      p:= `if`(n=1, 1, a(n-1));

      do p:= nextprime(p);

         if q(p-2) and q(p+2) then break fi

      od; p

    end:

seq(a(n), n=1..50);  # Alois P. Heinz, Dec 28 2018

PROG

(Java)

boolean isIsolatedPrime(int num){

    int upper = num + 2;

    int lower = num - 2;

    return isPrime(num) &&

          !isPrime(upper) &&

          !isPrime(lower) &&

          !isSemiPrime(upper) &&

          !isSemiPrime(lower);

   }

(PARI) is(n) = isprime(n) && bigomega(n + 2) > 2 && bigomega(n - 2) > 2 \\ David A. Corneth, Dec 28 2018

CROSSREFS

Cf. A000040, A001358, A007510, A134797.

Sequence in context: A178652 A119567 A142436 * A063645 A142607 A241045

Adjacent sequences:  A322839 A322840 A322841 * A322843 A322844 A322845

KEYWORD

nonn

AUTHOR

Kyle Buscaglia, Cory Baker, Dec 28 2018

STATUS

approved

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Last modified February 21 02:02 EST 2020. Contains 332086 sequences. (Running on oeis4.)