I write without ink, I vanish in rain, On black I am white, Yet leave no stain. What am I?

I cover ground but claim no land, And clouds rise only at my command.

Two, four, six, eight, Even numbers sequence great! Zero, then one, one and two, Fibonacci’s are nice too. But this sequence that I mean Starts: one, three, six, ten, fifteen. Don’t feel like a silly goose, just Try a cute or an obtuse guess.

Proud to be called A word like bald I fly, but am not a duck And appear on a buck

A pendulum pivoting around a single point, out on yonder playground as a popular pastime. Ah, how the youths propel themselves to such ponderously great heights.