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

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

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

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: A272861 A192690 A378082 * 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