|
%I #12 Mar 27 2021 14:57:44
%S 2,3,11,19,23,29,31,37,41,47,71,73,83,89,101,107,139,173,181,191,197,
%T 199,211,227,229,233,241,251,263,269,277,307,311,317,331,337,347,349,
%U 353,373,379,383,397,409,421,431,433,439,443,457,461,463,467,503,509
%N Primes p such that exactly one of the numbers 2p-3 and 2p+3 is prime.
%H Harvey P. Dale, <a href="/A172258/b172258.txt">Table of n, a(n) for n = 1..1000</a>
%e a(1)=2 because 2*2-3=1 (nonprime) and 2*2+3=7 (prime);
%e a(2)=29 because 2*29-3=55 (nonprime) and 2*29+3=61 (prime).
%p 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
%t Select[Prime[Range[100]],Total[Boole[PrimeQ[2#+{3,-3}]]]==1&] (* _Harvey P. Dale_, Mar 27 2021 *)
%Y Cf. A000040, A092110, A131426.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Jan 30 2010
%E Definition edited by _Emeric Deutsch_, Feb 15 2010
%E Corrected and extended by _Emeric Deutsch_, Feb 15 2010
|
