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A167771 Twice-isolated primes: primes p such that neither p+-2 nor p+-4 is prime. 4
2, 53, 89, 157, 173, 211, 251, 257, 263, 293, 331, 337, 359, 367, 373, 389, 409, 449, 479, 509, 541, 547, 557, 563, 577, 587, 593, 607, 631, 653, 683, 691, 701, 709, 719, 727, 733, 751, 787, 797, 839, 919, 929, 947, 953, 977, 983, 991, 997, 1039, 1069, 1103 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

2 together with primes p with property that (p-previous prime)>=6 and (next prime-p)>=6.

By the finitude of the generalized Brun constants, this sequence includes almost all primes.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

a(1)=2 (-2,0,4,6 are nonprimes); a(2)=53 (49,51,55,57 are nonprimes).

MATHEMATICA

Join[{2}, Select[Prime[Range[200]], NoneTrue[#+{4, 2, -2, -4}, PrimeQ]&]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 21 2016 *)

CROSSREFS

Cf. A007510, A137869.

Sequence in context: A179616 A200087 A139841 * A062853 A059703 A212889

Adjacent sequences:  A167768 A167769 A167770 * A167772 A167773 A167774

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Nov 11 2009

EXTENSIONS

Comment from Charles R Greathouse IV, Nov 12 2009

STATUS

approved

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Last modified September 21 23:55 EDT 2019. Contains 327286 sequences. (Running on oeis4.)