三角形、长方形和正方形数

GeoGebra 命令及参数

1. Sequence(Sequence[(i, j), i, j, n], j, 1, n) → triangularNumbers
2. Sequence(Sequence[(i, j), i, 1, n], j, 1, n) → squareNumbers
3. Sequence(Sequence[(i, j), i, 1, n], j, 1, n + 1) → oblongNumbers
4. Polygon((1, 1), (n, 1), (n, n), (1, 1)) → trianglePoly, f, g, h, i
5. Polygon((1, 2), (n, n + 1), (1, n + 1), (1, 2)) → oblongPoly, j, k, l, m
6. Polygon((1, 2), (n - 1, n), (1, n), (1, 2)) → squarePoly, p, q, r, s