"They won't start a fight, anyway."

"What is the Riddle of Tena's Ford?"

Elu explains the riddle. (The answer is probably an entire trigonometry textbook.)

A green is nerdsniped and sets about figuring it out on her everything.

She has a proof in ten minutes!

Elu would like to read her proof although perhaps it is in the wrong language for that.

It is totally in the wrong language for that but they can spend the next while talking math symbols and terminology so it can be translated.

They can!

...Either Elu isn't actually a mathematician or Sesat doesn't have notation for some of these things. (In fact it's both.)

Well, the nice thing about math notation is you can always break it down into smaller pieces! This green is happy to talk about math as long as Elu has patience for!

She starts running out of interest but it's not demanding of her ability to cram more things into her memory and it's plausibly an important step toward being able to understand other advances, besides which this riddle has practical implications in itself, so she doesn't ask to stop until they're done. But she's noticeably less enthusiastic after a couple of minutes.

The green will simplify so as to get through the whole explanation in a way that may not maximize comprehension but should at least be clear on there being well-described moving parts all the way down.

And when they feel they've learned enough Sesati the king will see them.

Sakasta Mashu, armed with reasonably decent machine translation, a yellow at one elbow and a green at the other to supplement, and her Sesati etiquette lesson, greets the Star of Stars in the fashion of a foreign diplomat.

"Sesat is pleased to welcome visitors from the stars. We would be delighted to hear what has brought you so far to meet us."

"Amentans have longed for generations to meet other kinds of people! It is one of our fondest ambitions to meet our neighbors and learn from one another! And most planets have not only no people, but no life at all, no water, no air - this one is so much like ours that it would even be possible for us to live alongside you! We chose this part of the planet because it is, so far as we could tell from the sky, the cleanest on the planet, which is a very worthy target of a people's attention and suggests a sympathy between us."

"We are interested in trading lore with our friends." There sure is an implication in there that they might specifically want to live here. He wonders why. "I have heard that your people have achieved such cleanliness, in fact, as surpasses even Sesat, and certainly that is a wonderful thing. I find myself wondering if your people have thus eliminated disease."

"Not all disease. Diseases that are eliminated - and we have done this for some - leave opportunities for any that are hardier and more complicated to arise. But our disease burden is lighter every generation, and while you are not just like us, many of the things we have learned will transfer to you."

"Impressive. How has that changed your society?"

"It is much safer! A baby born on Amenta today will probably live to be a hundred and fifty of your years or more."

He does some quick mental math to check his guess about what's going on here - that's a very high life expectancy but it doesn't mean more children per woman but it's, what, four times as many living grandparents? No, a baby born, if that's literal, if it's more than half of births - if it's more than half of births then... the replacement birth rate might be so low there's no need for any incentive beyond people's own desires. Definitely a good thing, if it's true, but a thing to be handled with care.

"It must be much easier to maintain your population under such circumstances."

"Is that a problem you have here?"

...He'll take that as confirmation.

"Sesat is well able to solve such problems."

"I would be so curious to hear how you do it! If there are spheres of work or commerce where your population is not balanced ideally, we would love to know so we can send the best visitors possible for you."

"Not only are those who have performed certain valuable services for Sesat and its king rewarded but so are any children they choose to claim. And of course there are other relevant policies. I am sure that whatever balance we might previously have preferred, it will change swiftly as we come to know you and learn your wisdom. Tell me, though: do you wish only to send us visitors to stay for a time and leave?"

"We would be absolutely delighted to buy some land so that some of us could live here indefinitely!"

"That may be possible to arrange. I expect land prices will be unstable in the near future until we have learned the lore your people spoke of to Elu and have begun to farm more efficiently; perhaps we should discuss that first."