OFFSET
2,1
COMMENTS
Also, the larger part in the Goldbach partition of 2n with the smallest difference between its prime parts.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 2..1000
Eric Weisstein's World of Mathematics, Goldbach Partition
Wikipedia, Goldbach's conjecture
FORMULA
a(n) = 2n - A112823(n).
EXAMPLE
a(9) = 11; the Goldbach partitions of 2(9) = 18 are (13,5) and (11,7). The partition with smaller difference between the primes is (11,7) (difference 4) and the larger part of this partition is 11.
MATHEMATICA
f[n_] := Block[{p = n/2}, While[! PrimeQ[p] || ! PrimeQ[n - p], p--];
n - p]; Table[f[n], {n, 4, 146, 2}]
PROG
(PARI) a(n) = {my(q = nextprime(n)); while (!isprime(2*n-q), q = nextprime(q+1)); q; } \\ Michel Marcus, Oct 22 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Dec 23 2013
STATUS
approved