2,1

Essentially the same as A002373, which does not have the a(2) term. - T. D. Noe, Sep 24 2007

a(n) = A171637(n,1). - Reinhard Zumkeller, Mar 03 2014

Conjecture: a(n) ~ O(n^1/2). - Jon Perry, Apr 29 2014

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

Index entries for sequences related to Goldbach conjecture

a(n) = n - A047949(n). - Jason Kimberley, Oct 09 2012

(PARI) A020481(n) = {local(np); np=1; while(!isprime(2*n-prime(np)), np++); prime(np)} \\ Michael B. Porter, Dec 11 2009

(PARI) A020481(n)=forprime(p=1, n, isprime(2*n-p)&return(p)) \\ M. F. Hasler, Sep 18 2012

(Haskell)

a020481 n = head [p | p <- a000040_list, a010051' (2 * n - p) == 1]

-- Reinhard Zumkeller, Jul 07 2014, Mar 03 2014

Cf. A020482.

Sequence in context: A064338 A197592 A103359 * A066660 A057957 A241686

Adjacent sequences: A020478 A020479 A020480 * A020482 A020483 A020484

nonn

David W. Wilson

approved