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Le Monde puzzle [#1087]

February 24, 2019
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Le Monde puzzle [#1087]

A board-like Le Monde mathematical puzzle in the digit category: Given a (k,m) binary matrix, what is the maximum number S of entries with only one neighbour equal to one? Solve for k=m=2,…,13, and k=6,m=8. For instance, for k=m=2, the matrix is producing the maximal number 4. I first attempted a brute force random filling

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call for sessions and labs at Bay2sC0mp²⁰

February 22, 2019
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call for sessions and labs at Bay2sC0mp²⁰

A call to all potential participants to the incoming BayesComp 2020 conference at the University of Florida in Gainesville, Florida, 7-10 January 2020, to submit proposals for contributed sessions on everything computational or training labs on a specific language or software. The deadline is April 1 and the sessions will

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simulation fodder for future exams

February 19, 2019
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simulation fodder for future exams

Here are two nice exercises for a future simulation exam, seen and solved on X validated.The first one is about simulating a Gibbs sampler associated with the joint target exp{-|x|-|y|-a(y-x|} defined over IR² for a≥0 (or possibly a__-1). The conditionals are identical and non-standard, but a simple bound on the conditional density is the corresponding

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Le Monde puzzle [#1085]

February 17, 2019
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Le Monde puzzle [#1085]

A new Le Monde mathematical puzzle in the digit category: Given 13 arbitrary relative integers chosen by Bo, Abigail can select any subset of them to be drifted by plus or minus one by Bo, repeatedly until Abigail reaches the largest possible number N of multiples of 5. What is the minimal possible value of

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Le Monde puzzle [#1083]

February 6, 2019
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Le Monde puzzle [#1083]

A Le Monde mathematical puzzle that seems hard to solve without the backup of a computer (and just simple enough to code on a flight to Montpellier): Given the number N=2,019, find a decomposition of N as a sum of non-trivial powers of integers such that (a) the number of integers in the sum is

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missing digit in a 114 digit number [a Riddler’s riddle]

January 30, 2019
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missing digit in a 114 digit number [a Riddler’s riddle]

A puzzling riddle from The Riddler (as Le Monde had a painful geometry riddle this week): this number with 114 digits 530,131,801,762,787,739,802,889,792,754,109,70?,139,358,547,710,066,257,652,050,346,294,484,433,323,974,747,960,297,803,292,989,236,183,040,000,000,000 is missing one digit and is a product of some of the integers between 2 and 99. By comparison, 76! and 77! have 112 and 114 digits, respectively. While 99! has 156 digits.

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more concentration, everywhere

January 24, 2019
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more concentration, everywhere

Although it may sound like an excessive notion of optimality, one can hope at obtaining an estimator δ of a unidimensional parameter θ that is always closer to θ that any other parameter. In distribution if not almost surely, meaning the cdf of (δ-θ) is steeper than for other estimators enjoying the same cdf at

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Le Monde puzzle [#1081]

January 23, 2019
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Le Monde puzzle [#1081]

A “he said-she said” Le Monde mathematical puzzle (again in the spirit of the famous Singapore high-school birthdate problem): Abigail and Corentin are both given a positive integer, a and b, such that a+b is either 19 or 20. They are asked one after the other and repeatedly if they are sure of the other’s

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Le Monde puzzle [#1076]

December 26, 2018
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Le Monde puzzle [#1076]

A cheezy Le Monde mathematical puzzle : (which took me much longer to find than to solve, as Warwick U does not get a daily delivery of the newspaper ): Take a round pizza (or a wheel of Gruyère) cut into seven identical slices and turn one

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running plot [and simulated annealing]

December 14, 2018
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running plot [and simulated annealing]

Last weekend, I found out a way to run updated plots within a loop in R, when calling plot() within the loop was never updated in real time. The above suggestion of including a Sys.sleep(0.25) worked perfectly on a simulated annealing example for deter...

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