1,1

The natural numbers can sequentially fill a right- or left-handed equilateral triangle. Componentwise addition of the values of these two triangles produces the present triangle.

The row sums for this triangle give A034262.

The difference between the right- and left-handed triangles produces A049581.

Table of n, a(n) for n=1..45.

Craig Knecht, Sum of right and left triangles.

Craig Knecht, Difference between right and left triangles A049581.

Displayed as a triangle:

2;

5 5;

10 10 10;

17 17 17 17;

26 26 26 26 26;

37 37 37 37 37 37;

...

Cf. A049581 (difference of triangles), A034262 (row sum of triangle), A069894 (center column).

Sequence in context: A059797 A173567 A288726 * A212624 A034387 A081240

Adjacent sequences: A265126 A265127 A265128 * A265130 A265131 A265132

nonn,tabl

Craig Knecht, Dec 02 2015

approved