A168064 Numbers n such that exactly one of n+-1 and n+-2 is prime.

0, 2, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20, 22, 24, 25, 27, 28, 29, 31, 32, 33, 35, 36, 38, 40, 41, 43, 44, 46, 48, 49, 51, 52, 54, 55, 57, 58, 59, 61, 62, 63, 65, 66, 68, 70, 71, 73, 74, 75, 77, 78, 80, 82, 84, 85, 87, 88, 90, 91, 95, 96, 98, 100, 101, 103, 104, 106, 107, 109

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 18 2009

Keywords

• nonn
• easy

Examples

			a(1)=0 (-2,-1 and 1 are nonprime, 2 is prime); a(2)=2 (0,1 and 4 are nonprime, 3 is prime); a(3)=7 (6,8 and 9 are nonprime, 5 is prime); a(4)=10 (8,9 and 12 are nonprime, 11 is prime); a(5)=11 (9,10 and 12 are nonprime, 13 is prime).
		

Links

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

Crossrefs

Cf. A000040, A100317, A141468.

Programs

Mathematica

Join[{0},Select[Range[120],Total[Boole[PrimeQ[#+{-2,-1,1,2}]]]==1&]] (* Harvey P. Dale, Apr 09 2020 *)

PARI

is(n)=isprime(n-2)+isprime(n-1)+isprime(n+1)+isprime(n+2)==1 \\ Charles R Greathouse IV, Jun 13 2017