Math Help - sum fof series?

How do we find the sum of the below series:
a)
1 + 1/3 + 1/6 + 1/10 + 1/15 + .........
b)
1/2 + 1/6 + 1/12 + 1/20 + ......

Thanks!!!

Originally Posted by a69356

How do we find the sum of the below series:
a)
1 + 1/3 + 1/6 + 1/10 + 1/15 + .........
b)
1/2 + 1/6 + 1/12 + 1/20 + ......

Thanks!!!

(b)






the series in (a) is just twice the sum of (b).