The Number Triangle obtained by starting with a row containing a single ``1'' and the next row containing three 1s and then letting subsequent row elements be computed by summing the elements above to the left, directly above, and above to the right:
See also Pascal's Triangle
References
Sloane, N. J. A. Sequence
A027907
in ``The On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html.