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A061708 Smallest number whose square has (2n - 1)^2 divisors. 0
1, 6, 36, 216, 210, 7776, 46656, 1260, 1679616, 10077696, 7560, 362797056, 44100, 18480, 78364164096, 470184984576, 272160, 264600, 101559956668416, 1632960, 3656158440062976, 21936950640377856, 180180, 789730223053602816, 9261000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) <= 36^(n-1); numbers of the latter form also have (2n-1)^2 divisors.

LINKS

Table of n, a(n) for n=1..25.

FORMULA

a(n) = Min_{x : d(x^2) = (2n-1)^2};

a(n) = Min_{x : A000005(A000290(x)) = A000290(A005408(n))}

EXAMPLE

n = 8, a(8) = 1260 = 2*2*3*3*5*7 and d(1260^2) = d(2*2*2*2*3*3*3*3*5*5*7*7) = (2*8 - 1)^2 = 15^2 = 225 n = 14, a(14) = 18480 and d(2*2*2*2*2*2*2*2*3*5*7*11) = (2n-1)^2 = 729.

CROSSREFS

Cf. A000005, A000290, A005179, A005408, A016017, A025281, A048691.

Sequence in context: A199525 A074436 A036162 * A216127 A124535 A267789

Adjacent sequences:  A061705 A061706 A061707 * A061709 A061710 A061711

KEYWORD

nonn

AUTHOR

Labos Elemer, Jun 19 2001

EXTENSIONS

More terms from David Wasserman, Jun 24 2002

STATUS

approved

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Last modified May 27 06:24 EDT 2019. Contains 323599 sequences. (Running on oeis4.)