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6:11 AM
A new tag: . Empty tag info. Wikipedia: Comma category, nLab: over category.
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Q: How does the functor $F: \textbf{C}/C \to \textbf{C}$ "forget about the base object" $C$?

Fruitful ApproachLet $\textbf{C}/C$ be a slice category with base object $C$. The functor that comes to mind is the one such that objects $f:X \to C$ are mapped to $X$, and arrows $a: X \to X'$ are mapped to themselves. Let $F$ be this mapping. Then since, the identiy on the object $f: X\to C$, is $1_X$, we ha...

 
 
8 hours later…
2:30 PM
@MartinSleziak I have at least created the very basic tag-excerpt and tag-wiki for . And I will remove the tag from the two questions which seem to be about Sirepinski triangle rather than about Sirepinski numbers.
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Q: Representing the areas of Sierpinski triangles as a partial sum of a geometric sequence?

gticecream8About Sierpinski triangles: Express the areas of the shaded triangles in the $n$th stage as a sum of a geometric series. How do I represent the increasing triangles as a partial sum of a geometric series? Sierpinski triangles: The Sierpinski triangle iterates an equilateral triangle (stage 0) b...

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Q: Find an non recursive function from recursive function

titansarusWe have $f(0) = 1 , f(1) = 4 , f(2) = 13 , f(n) = f(n-1) + 3^n$ (number of all of triangles in Sierpinski triangle) I want to find a non recursive function. I know the answer but I want a solution for it.

 
 
1 hour later…
3:32 PM
 

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