You are Oeis the Wise, professional Oracle. Your uncanny ability to predict how lists of whole numbers will continue – and only how lists of whole numbers will continue – creates infrequent but intense demand for your counsel: you usually leave your mountain home about once a month, whenever circumstances place a local noble or merchant lord in need of your services.
Today’s customer is Morgan, a monk. (Morgan has no money, but his temple has frequently provided you with food and shelter while travelling to more lucrative clients, so you’re fine doing this one for free.)
Morgan explains that he uses transcendental meditation to link himself to the substructure of the universe, observing the pulse and flicker of those lights which cast all we know as shadows. In his notes, he records flows of mana as they rise and ebb, forming the rhythms that undergird reality.
You tell him that sounds cool and you hope it works out for him.
However, Morgan continues, a recent supernova of unusual intensity has disrupted the leylines of the world, creating the possibility of flux in realms which have previously known only stasis. In ten days – day 384 in his record – he will have a once-in-several-lifetimes chance to not merely channel these flows, but change them: he plans to invoke two mana types simultaneously, wielding them in a ritual that subtly but profoundly reshapes the world for the better. If he is to do this, he must begin the endeavour now; to determine which sources of power he should prepare to conjure on that fateful day, he zealously entreats your assistance.
You tell him that sounds cool and you hope it works out for him. (Living alone on a mountain has not done wonders for your conversational repertoire.)
Morgan concludes by saying that his priorities for day 384 are as follows:
- Firstly, the strongest of the two mana types he channels cannot be Void, Doom, or Spite. These may be used if you are certain they will be the weaker of the pair, but if they dominate, darkness will possess him and he will transform into an immortal demon, wreaking horror and bloodshed upon the world he sought to improve.
- Secondly, the ritual must work. For this to occur, the two mana types together must have a combined power of at least 70.
- Finally, as a strictly tertiary objective, increasing the total amount of mana channelled would allow him to increase the amount of good done; however, this is much less important than guaranteeing the ritual works at all.
From the dedication in his eyes, you perceive Morgan will not be persuaded from this path: all you can do is ensure he walks it as best he can. You are Oeis the Wise, and you have a title to uphold. What, in your Oeisdom Wisdom, will you advise him to do?
I’ll be posting an interactive letting you test your decision, along with an explanation of how I generated the dataset, sometime next Friday on Monday the 23rd. I’m giving you a week, but the task shouldn’t take more than a few hours; use Excel, R, Python, Shivers, Inland Empire, Espirit de Corps, or whatever other tools you think are appropriate. Let me know in the comments if you have any questions about the scenario.
If you want to investigate collaboratively and/or call your decisions in advance, feel free to do so in the comments; however, please use spoiler tags or rot13 when sharing inferences/strategies/decisions, so people intending to fly solo can look for clarifications without being spoiled.
I observe that
solar seems to be (period 28) + (period 9) + (shortish upward transients) + (very small noise), and the periodic parts are predicted to be at 45 on day 384.
That's a good start. What about the others? Well,
lunar appears to be 75-solar, shifted by 14 days. On day 384 we expect it to be experiencing the reverse of solar's most recent upward transient; it will not be a good candidate for Morgan's purposes.
Annoyingly
ocean, breeze, flame, ash and earth all look rather unpredictable, except that ash is basically a scaled copy of the previous day's flame; none of them will be predictably at 25ish or more on day 384. I would be extremely unsurprised to find that some of these are more predictable than I think (e.g., breeze has a suspicious number of peaks at the same height and 6 or 7 days apart; maybe this is real, and maybe it's caused by something I could exploit with more work or ingenuity) but for now I'm leaving them alone. (Flame/ash also seems like it's not just uncorrelated random noise, but it might e.g. be low-pass-filtered noise.) Earth seems to have a pretty good chance of being big enough on any given day, but something more predictable would be better.
What about the bad ones?
Spite is perfectly predictable, being a sum of periodic spikes with periods 4, 5, 7, and 14; on dat 384 it will be zero. Void seems rather unpredictable, though its overall level isn't far off what we need -- but if we have to rely on luck we have better chances with earth than with void.
More helpfully,
doom has a strong periodic component of period 8 (and, alas, occasional single-day transients); its periodic component will be 30 on day 384. Unless we get unlucky with a sizeable negative transient, it seems like solar+doom is a likely winner.
Would this lead to danger of apocalypse?
It doesn't look like it. Solar is almost always bigger than doom; the largest doom-solar has ever been is 13, when our periodic estimates would have predicted an excess of 9; we are predicting solar=45 and doom=30 so we have plenty of slack to spare.
I don't see any obvious sign of
an abrupt change in the data that might correspond to the supernova.
Things I've been looking for:
Strong periodic components (either sinusoidal with any period, as found e.g. by FFT or periodogram calculations, or with integer period and arbitrary shape). Close correspondences between different kinds of mana, but I haven't looked for fancy things as opposed to the simple solar/lunar and flame/ash relationships. Short-term autocorrelation within a single type of mana. Long-term trends (no sign of any of these).
One notable thing I haven't bothered looking for:
Matches between either the raw data or the locations of peaks or troughs or anomalies, and things in the OEIS. (Despite our character's name.) That sort of thing would be amusing but feels like it would be a cheat even if it were there. Also, most OEIS sequences don't look much like random-ish noise.
So my advice to Morgan at present would be
to go for solar + doom
which will
almost certainly yield a total a little over 70, and almost certainly not cause a catastrophe; I think unexpectedly good outcomes are a bit more likely than unexpectedly bad ones.
Having read other answers, I add
that aphyer's suggestion looks strictly better than mine; annoyingly, I had noticed that there was some weak evidence of period-22 components in both earth and ocean but never bothered looking at their sum; in hindsight, eyeballing the plots of [EDITED to add for clarity: the sums of] all pairs of mana types with any chance of reaching 70 should have been a super-obvious thing to do, but I am a moron and didn't do that.