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Working with factors of triangular numbers.

• To: mathgroup at smc.vnet.net
• Subject: [mg78490] Working with factors of triangular numbers.
• From: Diana <diana.mecum at gmail.com>
• Date: Tue, 3 Jul 2007 05:23:30 -0400 (EDT)

Math folks,

I first generate a list of triangular numbers:

1, 3, 6, 10, 15, 21, ...

and then subtract one from each as:

0, 2, 5, 9, 14, 20, ...

I am trying to find the smallest triangular number (minus one) which
can be written as a product of "n" distinct factors, each factor > 1.

For example:

a(2) = 15, because 2*7 + 1 = 15.
a(3) = 55, because 2*3*9 + 1 = 55.

I have worked with Divisors and FactorInteger, but am getting bogged
down with repeated terms. Can someone think of a neat trick to work
this problem?

Diana M.

• Follow-Ups:
  • Re: Working with factors of triangular numbers.
    • From: "Diana Mecum" <diana.mecum@gmail.com>
  • Re: Working with factors of triangular numbers.
    • From: "Diana Mecum" <diana.mecum@gmail.com>
  • Re: Working with factors of triangular numbers.
    • From: "Diana Mecum" <diana.mecum@gmail.com>
  • Re: Working with factors of triangular numbers.
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>