A336629 a(n) is the least positive integer k such that it has exactly n triples of divisors (d1, d2, d3) such that they are pairwise coprime and d1 < d2 < d3 < 2*d1.

1, 60, 7140, 60060, 251940, 360360, 1369368, 1225224, 1531530, 7873866, 17687670, 5819814, 17160990, 11085360, 11741730, 19399380, 65564070, 9699690, 99533742, 85804950, 40562340, 90485220, 358888530, 504894390, 634956630, 531990690, 397687290, 512942430, 455885430, 514083570

Offset

0,2

Comments

Can we prove m is a divisor for all terms a(n) for n > N for some n? For example, are all terms from a(1) onwards divisible by 2?

For n > 0, it seems that 6|a(n) and a(n) is a Zumkeller number (A083207). Verified for n up to and including 29. - Ivan N. Ianakiev, Aug 02 2020

Links

Table of n, a(n) for n=0..29.

Example

a(3) = 60060 as 60060 = 28 * 39 * 55 = 33 * 35 * 52 = 35 * 39 * 44 and no positive integer < 60060 has exactly 3 such triples.

Crossrefs

Cf. A333966, A336628.

Sequence in context: A328951 A178785 A091753 * A303790 A327678 A130214

Adjacent sequences: A336626 A336627 A336628 * A336630 A336631 A336632

Keyword

nonn

Author

David A. Corneth, Jul 28 2020

Status

approved