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A062503 Squarefree numbers squared. 4
1, 4, 9, 25, 36, 49, 100, 121, 169, 196, 225, 289, 361, 441, 484, 529, 676, 841, 900, 961, 1089, 1156, 1225, 1369, 1444, 1521, 1681, 1764, 1849, 2116, 2209, 2601, 2809, 3025, 3249, 3364, 3481, 3721, 3844, 4225, 4356, 4489, 4761, 4900, 5041, 5329, 5476 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also, except for the initial term, numbers whose prime factors are squared. - Cino Hilliard, Jan 25 2006

a(n) = A000290(A005117(n)); A227291(a(n)) = 1. - Reinhard Zumkeller, Jul 07 2013

Also cubefree numbers that are squares. - Gionata Neri, May 08 2016

LINKS

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

FORMULA

n such that sumdiv(n, d, mu(d)*mu(n/d)) = 1 - Benoit Cloitre, Mar 03 2004

A000290 \ A062320. - R. J. Mathar, Jul 27 2013

a(n) ~ Pi^4/36 * n^2. - Charles R Greathouse IV, Nov 24 2015

MATHEMATICA

Select[Range[100], SquareFreeQ]^2

PROG

(PARI) je=[]; for(n=1, 200, if(issquarefree(n), je=concat(je, n^2), )); je

(PARI) n=0; for (m=1, 10^5, if(issquarefree(m), write("b062503.txt", n++, " ", m^2); if (n==1000, break))) \\ Harry J. Smith, Aug 08 2009

(PARI) is(n)=issquare(n, &n) && issquarefree(n) \\ Charles R Greathouse IV, Sep 18 2015

(Haskell)

a062503 = a000290 . a005117  -- Reinhard Zumkeller, Jul 07 2013

CROSSREFS

Cf. A005117. Characteristic function is A227291.

Sequence in context: A030140 A153158 A111245 * A248648 A063577 A087058

Adjacent sequences:  A062500 A062501 A062502 * A062504 A062505 A062506

KEYWORD

nonn

AUTHOR

Jason Earls (zevi_35711(AT)yahoo.com), Jul 09 2001

STATUS

approved

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Last modified July 24 16:43 EDT 2017. Contains 289775 sequences.