OFFSET
1,2
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..11631 (first 151 terms from Harry J. Smith)
Alberto Fraile, Roberto MartÃnez, and Daniel Fernández, Jacob's Ladder: Prime numbers in 2d, arXiv preprint arXiv:1801.01540 [math.HO], 2017. [They describe essentially the same sequence as A065358 except with offset 1 instead of 0, so their values for this sequence, which are given in A299300, differ by 1. - N. J. A. Sloane, Feb 20 2018]
Hans Havermann, Graph of first 30 million terms of A065358.
Hans Havermann, A064940 organized by axis crossing. The last number in a line is the axis crosser. Any number preceding it is a bouncer.
Don Reble, Table of n, a(n) for n = 1..97863 (The last term in the file is a(97863) = 694777169210.)
MAPLE
m:= -1:
t:= 0:
Res:= 0, 2:
for i from 3 to 5*10^7 by 2 do
if isprime(i) then m:= -m fi;
t:= t+2*m;
if t = 0 then Res:= Res, i+1 fi;
od:
Res; # Robert Israel, Feb 20 2018
MATHEMATICA
A065358 := Table[Sum[(-1)^(PrimePi[k]), {k, 1, n}], {n, 0, 500}]; Select[Range[300], A065358[[#]] == 0 &] - 1 (* G. C. Greubel, Feb 20 2018 *)
c = s = 0; k = 1; lst = {0}; While[k < 100000, c = Mod[c + Boole[PrimeQ[k]], 2]; s = s + (-1)^c; If[s == 0, AppendTo[lst, k]]; k++]; lst (* Robert G. Wilson v, Feb 20 2018 *)
PROG
(PARI) { n=s=0; for (m=1, 10^9, s+=(-1)^primepi(m); if (s==0, write("b064940.txt", n++, " ", m); if (n==150, return)) ) } \\ Harry J. Smith, Sep 30 2009
(Python)
from sympy import nextprime
A064940_list, p, d, n, r = [], 2, -1, 0, False
while n <= 10**6:
pn, k = p-n, d if r else -d
if 0 < k <= pn:
A064940_list.append(n+k-1)
d += -pn if r else pn
r, n, p = not r, p, nextprime(p) # Chai Wah Wu, Feb 21 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Oct 31 2001
EXTENSIONS
Initial term 0 added by N. J. A. Sloane, Feb 20 2018
STATUS
approved