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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.)