A131807 - OEIS

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A131807

Partial sums of A131377.

1, 2, 2, 3, 4, 4, 4, 5, 6, 7, 8, 8, 8, 9, 10, 11, 12, 12, 12, 13, 14, 15, 16, 16, 16, 16, 16, 16, 16, 17, 18, 18, 18, 18, 18, 18, 18, 19, 20, 21, 22, 22, 22, 23, 24, 25, 26, 26, 26, 26, 26, 26, 26, 27, 28, 29, 30, 31, 32, 32, 32, 33, 34, 35, 36, 37, 38, 38, 38, 38, 38, 39, 40, 40

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Table of n, a(n) for n=0..73.

MAPLE

P:=proc(n) local i, k, s; k:=1; s:=0; for i from 0 by 1 to n do if isprime(i) then if k=1 then k:=0; else k:=1; fi; fi; s:=s+k; print(s); od; end: P(100);

PROG

(PARI) a(n) = sum(m=0, n, (primepi(m) % 2) == 0) \\ Michel Marcus, Aug 15 2023

CROSSREFS

Cf. A131377.

Sequence in context: A006165 A078881 A336095 * A104351 A366274 A284511

Adjacent sequences: A131804 A131805 A131806 * A131808 A131809 A131810

KEYWORD

easy,nonn

AUTHOR

Paolo P. Lava and Giorgio Balzarotti, Jul 18 2007

STATUS

approved