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

1,2

Links

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

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 *)

Crossrefs

Cf. A013916, A013917, A013918.

Sequence in context: A289556 A086208 A090968 * A358547 A062736 A257716

Adjacent sequences: A020638 A020639 A020640 * A020642 A020643 A020644

Keyword

nonn

Author

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

Status

approved