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David Radcliffe
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David Radcliffe

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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

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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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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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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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Have him in circles
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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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Definitely not.
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Have him in circles
476 people
Vittoria Patti's profile photo
Ravikiran Gaikwad's profile photo
Jeffrey Rolland's profile photo
Renie Well's profile photo
Said Daily's profile photo
Constantino IV's profile photo
Lloyd Cledwyn's profile photo
cosmos re's profile photo
ANTHONY WRITER's profile photo
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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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