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A064523 Numbers n such that pi(n^2) is a square. 2
1, 3, 5, 10, 2640, 8304, 11699, 15330, 16810, 16910, 22463, 25906, 26652, 35950, 72429, 75470, 134141, 142413, 194711, 270353, 296073, 371964, 496254, 654609, 1640679, 1729409, 1854680, 4434965, 4973898, 5584120, 5783816 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(28) > 2*10^6. [Donovan Johnson, May 30 2010]
LINKS
EXAMPLE
n = 14: a(14) = 35950, Pi(35950^2) = Pi(1292402500) = 64866916 = 8054^2
MATHEMATICA
Do[ If[ IntegerQ[ Sqrt[ PrimePi[n^2]]], Print[n]], {n, 1, 400000} ]
lst = {}; Do[ If[ IntegerQ@ Sqrt@ PrimePi[n^2], AppendTo[lst, n]; Print@n], {n, 520000}]; lst (* Robert G. Wilson v, Feb 03 2006 *)
PROG
(PARI) pi(x, c=0) = forprime(p=2, x, c++); c for(n=1, 10^6, if(issquare(pi(n^2)), print1(n, " ")))
CROSSREFS
Cf. A000720, A115835 (square root of pi(a(n))).
Sequence in context: A354517 A354389 A297422 * A365443 A268034 A286567
KEYWORD
nonn
AUTHOR
Jason Earls, Oct 07 2001
EXTENSIONS
More terms from Robert G. Wilson v and Labos Elemer, Oct 08 2001
Further terms from Robert G. Wilson v, Oct 16 2001
a(20) from Robert G. Wilson v, Feb 03 2006
Added missing terms 134141, 142413, 194711 and a(24)-a(27) from Donovan Johnson, May 30 2010
a(28)-a(31) from Chai Wah Wu, Aug 27 2019
STATUS
approved

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Last modified July 18 12:51 EDT 2024. Contains 374378 sequences. (Running on oeis4.)