OFFSET
1,1
COMMENTS
a(n)<=2p(n)+2, where p(n) is the n-th prime.
The only even prime number, 2, is not able to be represented as a sum of two primes. - Lei Zhou, Apr 09 2014
LINKS
Lei Zhou, Table of n, a(n) for n = 1..10000
EXAMPLE
a(5)=20 since {2,3,5,7,11} can't represent 20 as a sum of two primes.
MATHEMATICA
a = {}; c = 6; Table[p = Prime[n]; Do[q = Prime[k]; If[sum = p + q; ! MemberQ[a, sum], AppendTo[a, sum]], {k, PrimePi[NextPrime[c - p, -1]], n}]; While[MemberQ[a, c], c = c + 2]; c, {n, 1, 100}] (*Lei Zhou, Apr 09 2014*)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ed T. Prothro (prothro(AT)compuserve.com), Jan 24 2004
EXTENSIONS
Flaw in the title fixed by Lei Zhou, Apr 09 2014
STATUS
approved