Hi all,(adsbygoogle = window.adsbygoogle || []).push({});

Im doing some work with the triangular numbers, pretty basic stuff:

1 3 6 10 15

Now im trying to understand how to get the formula for calculating the nth term +1, the formula is:

n(n+1)/2

I have tried doing a difference table, only to find that the second difference is 1, which lead me to think the forumla must start with 2N but this is incorrect. Please can someone show me the easiest method for working out basic sequence formulas.

Thanks,

Karla

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# Help with sequence formula

**Physics Forums | Science Articles, Homework Help, Discussion**