2,3

Terms are always even numbers because primes present in Goldbach partitions of n > 4 are odd and n = 4 has just one partition (2+2) where the difference is 0. a(n) = 0 iff n is prime. - Marcin Barylski, Apr 28 2018

Table of n, a(n) for n=2..89.

a[n_] := For[p=n, True, p--, If[PrimeQ[p]&&PrimeQ[2n-p], Return[2n-2p]]]

Cf. A065978, A066286, A303603. A002372.

Sequence in context: A158327 A136581 A175950 * A327873 A136665 A047765

Adjacent sequences: A066282 A066283 A066284 * A066286 A066287 A066288

nonn,easy

Dean Hickerson, Dec 12 2001

approved