Quote from: Yemmster on July 02, 2014, 05:11:32 PM

Quote from: Prospero on July 02, 2014, 04:52:26 PM

Quote from: Yemmster on July 02, 2014, 04:49:55 PM

According to Wolfram Alpha, it's not a triangular number. Sad

http://www.wolframalpha.com/input/?i=is+2147129+a+triangular+number%3F

"if the positive triangular root n of x is an integer, then x is the nth triangular number"

$ bc
((8 * 2147129 + 1) -1 )/2
8588516.00000000000000000000

I have to challenge your result here Prospero, sorry about that. Dug out my old mathbooks from the university to verify, it might still be wrong though so if someone else could verify it Please do.

http://i.imgur.com/d90yvj2.png

Yemmster: Your answer is not an integer. So does that mean its a dead end