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David Radcliffe

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### David Radcliffe

Shared publicly -David Radcliffe originally shared:

I presented a talk tonight at the Twin Cities R User Group. The talk showed how to use R to scrape data from a website, look up latitudes and longitudes, and display it on an interactive map, using Walmart store closings as an example. I hope that it is useful for other people who are creating interactive maps.

Password. Sign In Cancel. RPubs. brought to you by RStudio. Sign in Register. Mapping Walmart store closures in R; by David Radcliffe; Last updated about 19 hours ago. Hide Comments (–) Share Hide Toolbars. ×. Post on: Twitter Facebook Google+. Or copy & paste this link into an email or IM:

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### David Radcliffe

Shared publicly -I wrote a little JavaScript application to play the game of Nim. Enjoy! http://convex.org/nim/

The Game of Nim. Set up the board by clicking on the gray squares. Click on the Move button when you are ready to play. Then you and the computer will take turns removing the blue boxes. Clicking on a blue box will remove that box, and all boxes directly above it. The player that removes the ...

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### David Radcliffe

Shared publicly -The Franklin graph shows the connections between the 12 different ways to express a+b+c. Each edge represents an application of the commutative or transitive law. Was this known previously?

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Wow, very interesting!

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### David Radcliffe

Shared publicly -Do the frequencies of Emoji characters follow Zipf's law?

Emojitracker.com is a very interesting site that tracks how often each emoji is used on Twitter. The statistics are updated in real time, and it's really quite amazing to watch. (In case the reader...

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### David Radcliffe

Shared publicly -I am investigating the sum of digits of 2^n. I have discovered an elementary proof that s(2^n) > log_4 n for all n. What is the best known lower bound for this sequence?

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Ah. In that case, I have discovered an elementary proof that s(2^n) is bounded.

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### David Radcliffe

Shared publicly -I thought I'd share my results on a fun math problem. Suppose that an infection spreads among the squares of a checkerboard in such a manner that a square with three infected neighbors becomes infected itself. What is the smallest number of squares that must be infected initially for the infection to spread to the entire board?

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### David Radcliffe

Shared publicly -Interactive visual proof that every pentagonal number is 1/3 of a triangular number.

Triangular and pentagonal numbers. This applet illustrates the theorem that every pentagonal number is one-third of a triangular number. Drag the slider to change the size of the triangle. N = 8.

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### David Radcliffe

Shared publicly -I wrote a blog post discussing a question of Kurt Mahler: Which squares have only the digits 0 or 1 when written in base 5? I found all such squares less than 5^64 and proved that infinitely many are not divisible by 5.

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### David Radcliffe

Shared publicly -This is a directed graph with 1000 vertices, numbered from 0 to 999, and a directed edge from vertex n to vertex (n*n+2) mod 1000 for each n. I think it's rather pretty.

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great work thank you david

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Introduction

I am a college math instructor living in St. Paul MN. I am not a vice president at Google; that is a different David Radcliffe. I did not star in the Harry Potter movies; that is Daniel Radcliffe.

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