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

3, 5, 13, 19, 29, 31, 41, 43, 53, 59, 61, 71, 73, 83, 89, 97, 101, 103, 109, 127, 131, 137, 139, 151, 163, 167, 173, 179, 181, 193, 199, 223, 227, 229, 239, 241, 257, 263, 269, 271, 281, 283, 307, 311, 313, 331, 337, 347, 349, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421

Offset

1,1

Comments

This is the complement of A088176 in the set of odd primes. - R. J. Mathar, Jul 04 2013

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Formula

a(n) ~ prime(n) ~ n log n. - Charles R Greathouse IV, Jun 28 2013

Example

a(1) = 3 because 3 is prime and prevprime(3) - 2 = 2 - 2 = 0 is not prime,
a(2) = 5 because 5 is prime and prevprime(5) - 2 = 3 - 2 = 1 is not prime,
a(3) = 13 because 13 is prime and prevprime(13) - 2 = 11 - 2 = 9 is composite.

Mathematica

Select[Prime[Range[2, 100]], Not[PrimeQ[NextPrime[#, -1] - 2]] &] (* Alonso del Arte, Jul 04 2013 *)

Prog

(PARI) is(n)=n>2 && !isprime(precprime(n-2)-2) && isprime(n) \\ Charles R Greathouse IV, Mar 18 2014

Crossrefs

Cf. A088175, A088176.

Sequence in context: A157468 A191017 A228228 * A157974 A019420 A306930

Adjacent sequences: A227028 A227029 A227030 * A227032 A227033 A227034

Keyword

nonn

Author

Irina Gerasimova, Jun 28 2013

Status

approved