cp's OEIS Frontend

A227031 Odd primes such that the previous prime is not the larger part of a twin prime pair.

%I A227031 #27 Mar 18 2014 01:44:32
%S A227031 3,5,13,19,29,31,41,43,53,59,61,71,73,83,89,97,101,103,109,127,131,
%T A227031 137,139,151,163,167,173,179,181,193,199,223,227,229,239,241,257,263,
%U A227031 269,271,281,283,307,311,313,331,337,347,349,359,367,373,379,383,389,397,401,409,419,421
%N A227031 Odd primes such that the previous prime is not the larger part of a twin prime pair.
%C A227031 This is the complement of A088176 in the set of odd primes. - _R. J. Mathar_, Jul 04 2013
%H A227031 Charles R Greathouse IV, <a href="/A227031/b227031.txt">Table of n, a(n) for n = 1..10000</a>
%F A227031 a(n) ~ prime(n) ~ n log n. - _Charles R Greathouse IV_, Jun 28 2013
%e A227031 a(1) = 3 because 3 is prime and prevprime(3) - 2 = 2 - 2 = 0 is not prime,
%e A227031 a(2) = 5 because 5 is prime and prevprime(5) - 2 = 3 - 2 = 1 is not prime,
%e A227031 a(3) = 13 because 13 is prime and prevprime(13) - 2 = 11 - 2 = 9 is composite.
%t A227031 Select[Prime[Range[2, 100]], Not[PrimeQ[NextPrime[#, -1] - 2]] &] (* _Alonso del Arte_, Jul 04 2013 *)
%o A227031 (PARI) is(n)=n>2 && !isprime(precprime(n-2)-2) && isprime(n) \\ _Charles R Greathouse IV_, Mar 18 2014
%Y A227031 Cf. A088175, A088176.
%K A227031 nonn
%O A227031 1,1
%A A227031 _Irina Gerasimova_, Jun 28 2013