OFFSET
2,2
COMMENTS
That is, number of numbers of the form prime(i) + prime(j) with 1 <= i < j <= n, where prime(k) = k-th prime. - N. J. A. Sloane, Jun 05 2015
LINKS
Zak Seidov, Table of n, a(n) for n = 2..1000
EXAMPLE
For n = 5, the sums are 5, 7, 8, 9, 10, 12, 13, 14, 16, 18. - N. J. A. Sloane, Jun 05 2015
PROG
(PARI) a(n)={my(pr=primes(n), sums=Set()); for(i=1, n-1, for(j=i+1, n, s=pr[i]+pr[j]; sums=setunion(sums, Set(s))); ); length(sums); } \\ Michel Marcus, Oct 02 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Name edited by Petros Hadjicostas, Nov 19 2019
STATUS
approved