login
Greatest p with p, q both prime, p+q = 2n.
29

%I #19 Sep 04 2024 13:13:39

%S 2,3,5,7,7,11,13,13,17,19,19,23,23,23,29,31,31,31,37,37,41,43,43,47,

%T 47,47,53,53,53,59,61,61,61,67,67,71,73,73,73,79,79,83,83,83,89,89,89,

%U 79,97,97,101,103,103,107,109,109,113,113,113,109,113,113,109,127,127,131,131

%N Greatest p with p, q both prime, p+q = 2n.

%C a(n) = A171637(n,A035026(n)). - _Reinhard Zumkeller_, Mar 03 2014

%H H. J. Smith, <a href="/A020482/b020482.txt">Table of n, a(n) for n = 2..20000</a>

%t a[n_] := {p, q} /. {ToRules @ Reduce[p+q == 2*n, {p, q}, Primes]} // Max; Table[a[n], {n, 2, 100}] (* _Jean-François Alcover_, Dec 19 2013 *)

%t Table[Max[Flatten[Select[IntegerPartitions[2n,{2}],AllTrue[#,PrimeQ]&]]],{n,2,70}] (* _Harvey P. Dale_, Sep 04 2024 *)

%o (Haskell)

%o a020482 = last . a171637_row -- _Reinhard Zumkeller_, Mar 03 2014

%o (PARI) a(n)=forprime(q=2,n,if(isprime(2*n-q), return(2*n-q))) \\ _Charles R Greathouse IV_, Apr 28 2015

%Y Cf. A060264, A020481.

%K nonn

%O 2,1

%A _David W. Wilson_