A020482 Greatest p with p, q both prime, p+q = 2n.

2, 3, 5, 7, 7, 11, 13, 13, 17, 19, 19, 23, 23, 23, 29, 31, 31, 31, 37, 37, 41, 43, 43, 47, 47, 47, 53, 53, 53, 59, 61, 61, 61, 67, 67, 71, 73, 73, 73, 79, 79, 83, 83, 83, 89, 89, 89, 79, 97, 97, 101, 103, 103, 107, 109, 109, 113, 113, 113, 109, 113, 113, 109, 127, 127, 131, 131

Offset: 2

Author

David W. Wilson

Keywords

• nonn

Comments

a(n) = A171637(n,A035026(n)). - Reinhard Zumkeller, Mar 03 2014

Links

• H. J. Smith, Table of n, a(n) for n = 2..20000

Crossrefs

Cf. A060264, A020481.

Programs

Haskell

a020482 = last . a171637_row  -- Reinhard Zumkeller, Mar 03 2014

Mathematica

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

PARI

a(n)=forprime(q=2,n,if(isprime(2*n-q), return(2*n-q))) \\ Charles R Greathouse IV, Apr 28 2015

Python

from sympy import primerange, isprime
def A020482(n): return next(m for p in primerange(2*n) if isprime(m:=(n<<1)-p)) # Chai Wah Wu, Nov 19 2024