%I #24 Nov 20 2019 01:41:57

%S 1,3,6,10,13,17,21,25,29,35,39,45,50,54,59,63,70,75,81,86,91,97,102,

%T 109,114,119,125,130,135,143,148,154,162,168,175,181,187,195,200,206,

%U 213,218,224,230,236,242,249,258,263

%N a(n) is the number of distinct sums of 2 different primes chosen from the first n primes.

%C 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

%H Zak Seidov, <a href="/A049880/b049880.txt">Table of n, a(n) for n = 2..1000</a>

%e For n = 5, the sums are 5, 7, 8, 9, 10, 12, 13, 14, 16, 18. - _N. J. A. Sloane_, Jun 05 2015

%o (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

%Y Cf. A000040, A049881, A049882, A253250 (first differences).

%K nonn

%O 2,2

%A _Clark Kimberling_

%E Name edited by _Petros Hadjicostas_, Nov 19 2019