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A172258
Primes p such that exactly one of the numbers 2p-3 and 2p+3 is prime.
1
2, 3, 11, 19, 23, 29, 31, 37, 41, 47, 71, 73, 83, 89, 101, 107, 139, 173, 181, 191, 197, 199, 211, 227, 229, 233, 241, 251, 263, 269, 277, 307, 311, 317, 331, 337, 347, 349, 353, 373, 379, 383, 397, 409, 421, 431, 433, 439, 443, 457, 461, 463, 467, 503, 509
OFFSET
1,1
LINKS
EXAMPLE
a(1)=2 because 2*2-3=1 (nonprime) and 2*2+3=7 (prime);
a(2)=29 because 2*29-3=55 (nonprime) and 2*29+3=61 (prime).
MAPLE
a := proc (n): if isprime(n) = true and isprime(2*n-3) = true and isprime(2*n+3) = false then n elif isprime(n) = true and isprime(2*n-3) = false and isprime(2*n+3) = true then n else end if end proc: seq(a(n), n = 1 .. 700); # Emeric Deutsch, Feb 15 2010
MATHEMATICA
Select[Prime[Range[100]], Total[Boole[PrimeQ[2#+{3, -3}]]]==1&] (* Harvey P. Dale, Mar 27 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Definition edited by Emeric Deutsch, Feb 15 2010
Corrected and extended by Emeric Deutsch, Feb 15 2010
STATUS
approved