[seqfan] Re: A new sequence in Dutch magazine "Pythagoras"

Jon Schoenfield jonscho at hiwaay.net
Fri Dec 2 01:30:12 CET 2016


I don't know Dutch, but copying the text from the first page (i.e., the one 
numbered 20, but it's page 22 of the PDF) into the Bing Translator and 
attempting to correct the grammar in its output (and taking some guesses in 
places where that output it made very little sense to me), I got the 



In the September issue we wrote a competition as part of our series on 
integer sequences. In this latest issue of volume 55 we give the result.

by Matthijs Coster


Contest Results

Keep in mind that a best original integer sequence still has not appeared in 
the Online Encyclopedia of Integer Sequences (OEIS). That was the Mission of 
the price question we wrote in September. Also there was a New Year's 
challenge: create a sequence containing the number 2016. We wrote about this 
bonus question in the February issue.

The most beautiful entry – without the restriction that 2016 must be in it – 
according to the jury was an integer sequence from Pim Sailor (Gymnasium 
Sorghvliet, The Hague). It is the sequence

   1, 3, 5, 8, 11, 14, 17, 21, 24, 28, 32, 36, 40, 44, 49, 53, 57, 62, 66, 
71, 75, 80, 84, 90, 94, 99, ...

If you do not see the system behind it as soon as you see this sequence, 
don't worry, because what Pim has figured out is certainly resourceful. Pim 
based it on a variant on the game Battleship. The sea is divided into n 
areas. You have n^2 ships available to you that can apportion among these n 
areas. Your opponent may look at the way you have apportioned your ships and 
then decide to completely bomb any one area. All ships in that area are then 
destroyed. If you are smart, you'll spread the ships as evenly as possible 
among the n areas. However, in your first move, you will lose n ships. You 
will then reapportion the remaining ships among the n areas. What Pim 
wondered was: how many bombings are required in order to destroy all ships? 
Let's look at an example with n = 5 (see illustration). The sea is divided 
into 5 areas in which your 25 ships must be apportioned. The sequence of 
numbers of remaining ships is as follows: 25, 20, 16, 12, 9, 7, 5, 4, 3, 2, 
1, 0. After 11 bombings, all ships are destroyed. So, a_5 = 11.


Can we predict the numbers in Pim's sequence? That works pretty reasonably. 
Let's begin again with n areas. It is quite difficult to determine the exact 
value of a_n but we can give an approximation. Let us begin, not with n^2 
ships, but with n ships. It is clear that only after n bombings are all 
ships destroyed. If we start with 2n ships, then after the first (1/2)n 
bombings, n ships are destroyed.


I was going to go on and try to (very roughly!) translate the next page, but 
I realized at the bottom of the above (very rough!) translation of the first 
page that I didn't understand the last paragraph above.  If n=5 and we start 
with 2n = 10 ships, what does it mean to say that "after the first (1/2)n 
bombings, n ships are destroyed"?  "The first (1/2)n bombings" are the first 
2.5 bombings, and it's hard to have a nonintegral number of bombings!  :-)

(I think what it means is that Bing Translator and I together did not come 
up with a reliable translation....)  :-(

-- Jon

----- Original Message ----- 
From: "Neil Sloane" <njasloane at gmail.com>
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Sent: Thursday, December 01, 2016 2:00 PM
Subject: [seqfan] A new sequence in Dutch magazine "Pythagoras"

> Dear Sequence Fans, In the June 2016 issue of Pythagoras
> on pages 20 and 21 there is a new sequence from Pim Spelier.
> See http://www.pyth.eu/jaargangen/Pyth55-6.pdf
> It looks like Pythagoras had a competition to
> find the best sequence not in the OEIS,
> and this was the winner.  I think we should
> add it to the OEIS, but my Dutch is not good enough
> to give a clear definition.
> Maybe someone who speaks Dutch would be willing to submit the sequence (if
> so, please tell me the A-number).
> Thanks to Omar Pol who found the magazine (there is also an article about
> the toothpick sequence A139250).
> --
> Seqfan Mailing list - http://list.seqfan.eu/

More information about the SeqFan mailing list