|
%I #16 Feb 03 2018 09:53:52
%S 7,19,31,55,91,139,175,199,211,379,391,451,499,535,631,715,919,931,
%T 1039,1135,1291,1315,1399,1435,1639,1711,1759,1819,1855,1891,1939,
%U 2179,2215,2359,2431,2515,2575,2719,2731,2899,2971,3115,3271,3691,3775,3955,4195
%N Numbers x of the form x = 2*y - 3 = 3*z - 2 where y and z are primes.
%e a(1)=7 because 5*2 - 3 = 3*3 - 2;
%e a(2)=19 because 11*2 - 3 = 7*3 - 2.
%p isA169605 := proc(x) if type(x+3,'even') then if (x+2) mod 3 = 0 then isprime( (x+3)/2) and isprime((x+2)/3) ; else false ; end if else false; end if; end proc: for x from 1 to 10000 do if isA169605(x) then printf("%d,",x) ; end if; end do: # _R. J. Mathar_, Jan 27 2010
%t Select[3Prime[Range[250]]-2,PrimeQ[(3+#)/2]&] (* _Harvey P. Dale_, May 11 2011 *)
%o (Sage)
%o is_prime_Q = lambda x: x.is_integral() and Integer(x).is_prime()
%o A169605 = list(x for x in range(1, 10**4) if is_prime_Q((x+3)/2) and
%o is_prime_Q((x+2)/3))
%o A169605[:36]
%o # _D. S. McNeil_, Dec 21 2009
%Y Cf. A000040, A131426.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Dec 03 2009
%E Corrected and extended by _Jim Nastos_ and _D. S. McNeil_, Dec 21 2009
%E A few more terms from _R. J. Mathar_, Jan 27 2010
|
