28 is the smallest triangular number to have over five divisors (1,2,4,7,14,28).
What is the value of the smallest triangular number to have
over one hundred divisors? ... over two hundred divisors?
Based on a problem from Project Euler.
Not being a programmer I first checked this:
https://oeis.org/A063440
the number of divisors of each triangular number
you can easily scan to find the 384th triangular number has 112 factors and 2015th has 240.
(I thought the second interesting because it is the current year.)
but searching manually was a bit tough so I found the sequence of record breakers:
https://oeis.org/A101755
The last number given is the 281690531199th triangular number. I just checked and it has 387072 divisors.

Posted by Jer
on 20151211 13:22:25 