Search a number
oban n.  and  triangular n.

Search a number

(max 15 digits)

First numbers that belong to both sets:

3, 6, 10, 15, 28, 36, 55, 66, 78, 300, 325, 378, 528, 595, 630, 666, 703, 780, 820, 903, 990.