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A064499 Composite numbers n such that product of aliquot divisors of n is a perfect square. 1

%I

%S 12,16,18,20,28,32,44,45,48,50,52,63,68,75,76,80,81,92,98,99,112,116,

%T 117,124,147,148,153,162,164,171,172,175,176,180,188,192,207,208,212,

%U 236,242,243,244,245,252,256,261,268,272,275,279,284,288,292,300,304

%N Composite numbers n such that product of aliquot divisors of n is a perfect square.

%H Harry J. Smith, <a href="/A064499/b064499.txt">Table of n, a(n) for n = 1..1000</a>

%t Do[ If[ !PrimeQ[n] && IntegerQ[ Sqrt[ Apply[ Times, Delete[ Divisors[n], -1]]]], Print[n]], {n, 2, 500} ]

%o (PARI) pad(n)=my(d=divisors(n), p=1); for (i=1, #d-1, p*=d[i]); p

%o n=0; for (m=2, 10^9, if (!isprime(m) && issquare(pad(m)), write("b064499.txt", n++, " ", m); if (n==1000, break))) \\ _Harry J. Smith_, Sep 16 2009

%o (PARI) is(n)=!isprime(n) && (ispower(n,4) || numdiv(n)%4==2) && n>1 \\ _Charles R Greathouse IV_, Oct 17 2015

%Y Cf. A048699, A007956.

%K base,easy,nonn

%O 1,1

%A _Robert G. Wilson v_, Oct 05 2001

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Last modified July 21 04:40 EDT 2019. Contains 325189 sequences. (Running on oeis4.)