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A064499 Composite numbers n such that product of aliquot divisors of n is a perfect square. 1
12, 16, 18, 20, 28, 32, 44, 45, 48, 50, 52, 63, 68, 75, 76, 80, 81, 92, 98, 99, 112, 116, 117, 124, 147, 148, 153, 162, 164, 171, 172, 175, 176, 180, 188, 192, 207, 208, 212, 236, 242, 243, 244, 245, 252, 256, 261, 268, 272, 275, 279, 284, 288, 292, 300, 304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

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

PROG

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

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

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

CROSSREFS

Cf. A048699, A007956.

Sequence in context: A119911 A272861 A192690 * A080258 A054290 A107308

Adjacent sequences:  A064496 A064497 A064498 * A064500 A064501 A064502

KEYWORD

base,easy,nonn

AUTHOR

Robert G. Wilson v, Oct 05 2001

STATUS

approved

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Last modified June 20 05:01 EDT 2019. Contains 324229 sequences. (Running on oeis4.)