OFFSET

0,1

COMMENTS

Except for first two terms, same as A001172.

The first occurrence of k in A045917.

The graph looks like a comet. - Daniel Forgues, Jun 12 2014

LINKS

Robert G. Wilson v, Table of n, a(n) for n = 0..10000 (first 1001 terms from T. D. Noe)

EXAMPLE

a(3) = 22 as 22 = (19+3) = (17+5) = (11+11). There are exactly 3 ways 22 can be expressed as the sum of two primes and no even number less than 22 can be so expressed.

From Daniel Forgues, Jun 13 2014: (Start)

Terms for n = 1..6 and corresponding sums:

a(1) = 4 = 2 + 2;

a(2) = 10 = 7 + 3 = 5 + 5;

a(3) = 22 = 19 + 3 = 17 + 5 = 11 + 11;

a(4) = 34 = 31 + 3 = 29 + 5 = 23 + 11 = 17 + 17;

a(5) = 48 = 43 + 5 = 41 + 7 = 37 + 11 = 31 + 17 = 29 + 19;

a(6) = 60 = 53 + 7 = 47 + 13 = 43 + 17 = 41 + 19 = 37 + 23 = 31 + 29.

(End)

MATHEMATICA

f[n_] := Length@ Select[2n - Prime@ Range@ PrimePi@ n, PrimeQ]; nn = 100; t = Table[0, {nn}]; k = 1; cnt = 0; While[cnt < nn, a = f@k; If[a <= nn && t[[a]] == 0, t[[a]] = 2 k; cnt++]; k++]; t (* Robert G. Wilson v, Mar 15 2011 *)

CROSSREFS

KEYWORD

nonn,look

AUTHOR

David W. Wilson, Jun 14 1998

STATUS

approved