A061568 Number of primes <= sum of first n primes.

1, 3, 4, 7, 9, 13, 16, 21, 25, 31, 37, 45, 51, 60, 66, 75, 85, 95, 103, 115, 127, 138, 150, 162, 177, 191, 205, 219, 233, 250, 267, 283, 300, 319, 338, 360, 376, 400, 421, 441, 461, 481, 509, 531, 557, 578, 602, 630, 653, 684, 707, 737, 765, 793, 825, 853, 884

Offset: 1

Author

Harvey P. Dale, May 18 2001

Keywords

• easy
• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000849, A000720, A007504.

Programs

Mathematica

PrimePi/@FoldList[Plus, 0, Prime[Range[50]]]//Rest

PARI

{ default(primelimit, 3682913); n=0; s=0; forprime (p=2, prime(1000), s+=p; write("b061568.txt", n++, " ", primepi(s)) ) } \\ Harry J. Smith, Jul 24 2009

PARI

a(n) = primepi(sum(k=1, n, prime(k))); \\ Michel Marcus, Jul 02 2018

Formula

a(n) = A000720(A007504(n)). - Michel Marcus, Jul 02 2018