2 * n is easy. 3 * n is easy, just multiply by 2 and add one n. 4 is easy, just multiply by 2, two times (or multiply by 5 and subtract one n). 5 is easy. Six i

2 * n is easy. 3 * n is easy, just multiply by 2 and add one n. 4 is easy, just multiply by 2, two times (or multiply by 5 and subtract one n). 5 is easy. Six is easy, just multiply by 5 and add one n. 9 is easy, just multiply by 10 and subtract one n. But 7 and 8 are not 'reachable' with two operations.