A020641 a(n)-th prime is sum of first k primes for some k.

1, 3, 7, 13, 45, 60, 977, 1108, 2470, 2687, 2784, 3126, 3470, 3977, 4100, 4511, 4644, 5668, 6148, 6627, 6963, 8407, 9767, 10379, 11007, 11220, 11449, 12111, 12332, 23080, 25001, 28009, 28357, 28709, 29060, 29404, 30824, 32271, 33397, 33764, 47735, 52278

Offset: 1

Author

N. J. A. Sloane, Renaud Lifchitz (100637.64(AT)CompuServe.COM), David W. Wilson

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..2500

Crossrefs

Cf. A013916, A013917, A013918.

Programs

Mathematica

PrimePi /@ Select[ FoldList[Plus, 0, Prime@ Range@450], PrimeQ@# &] (* Robert G. Wilson v Sep 28 2006 *)
PrimePi/@Select[Accumulate[Prime[Range[500]]],PrimeQ] (* Harvey P. Dale, Jun 05 2013 *)