%I #13 Oct 31 2013 12:17:13
%S 1,3,7,13,45,60,977,1108,2470,2687,2784,3126,3470,3977,4100,4511,4644,
%T 5668,6148,6627,6963,8407,9767,10379,11007,11220,11449,12111,12332,
%U 23080,25001,28009,28357,28709,29060,29404,30824,32271,33397,33764,47735,52278
%N a(n)-th prime is sum of first k primes for some k.
%H Harvey P. Dale, <a href="/A020641/b020641.txt">Table of n, a(n) for n = 1..2500</a>
%t PrimePi /@ Select[ FoldList[Plus, 0, Prime@ Range@450], PrimeQ@# &] (* _Robert G. Wilson v_ Sep 28 2006 *)
%t PrimePi/@Select[Accumulate[Prime[Range[500]]],PrimeQ] (* _Harvey P. Dale_, Jun 05 2013 *)
%Y Cf. A013916, A013917, A013918.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Renaud Lifchitz (100637.64(AT)CompuServe.COM), _David W. Wilson_