cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A061708 Smallest number whose square has (2n - 1)^2 divisors.

Original entry on oeis.org

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, 58786560, 170581728179578208256
Offset: 1

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Author

Labos Elemer, Jun 19 2001

Keywords

Comments

a(n) <= 6^(n-1); 36^(n-1) has (2n-1)^2 divisors for all n.

Examples

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

Crossrefs

Formula

a(n) = Min_{x : d(x^2) = (2n-1)^2};
a(n) = Min_{x : A000005(A000290(x)) = A000290(A005408(n))}.

Extensions

More terms from David Wasserman, Jun 24 2002
Edited by Charlie Neder, Jun 03 2019
a(26)-a(27) from Amiram Eldar, Dec 03 2023