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Easy Sequences 27: Product of Radicals of Integers
The radical of a positive integer is defined as the product of the distinct prime numbers dividing . For example, the distinct ...

2 months ago

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Easy Sequences 31: N-N's Sequence
We define the N-N's Sequence, as the series of all positive integers in ascending order and with repetition, wherein any number ...

2 months ago

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Easy Sequences 25: Product of Series
The function 'P(n)' is defined as the series product: where 'T(n)' is the triangular sum: ...

2 months ago

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Easy Sequences 24: Number of Coprime Lattice Points
Given a number 'n', you were tasked to mark and count all coprime lattice points at the first quadrant bounded by the points (0,...

2 months ago

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Easy Sequences 23: Hat Guessing Game!
Consider the following Game Show: Hats, with numbers written on each, were placed on the heads of the participants. Participant...

2 months ago

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Easy Sequences 18: Set Bits of Triple Summations
The function S(n) is defined by the following triple summations: The double brackets mean that th...

2 months ago

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Easy Sequences 21: Combinatorial Summations
Create the function S(n), defined by the following summation: The symbol is the combination f...

2 months ago

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Easy Sequences 16: Volume of Embedded Octahedron
An octahedron (not regular) is formed by joining the centers of the faces of a rectangular parallelepiped (see below figure). ...

2 months ago

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Easy Sequences 13: Average Speed of Spaceship
A certain alien spaceship is capable of traveling at extremely high velocities and is able to change speed instantaneously. The ...

2 months ago

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Easy Sequences 12: 50th Prime
Write a function that outputs the th prime after a given number . For example, the th prime after is . NOTE: If itself is pr...

2 months ago

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Easy Sequences 10: Sum of Cumsums of Fibonacci Sequence
The function F(n) is defined as the set of Fibonacci numbers from the first up to the n-th. S(n) is the result of applying to F,...

2 months ago

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Easy Sequences 9: Faithful Pairs
A "faithful number" is a non-prime number that is one less or one more than some prime number but not both. For example, for num...

2 months ago

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Easy Sequences 5: Project Euler Problem 1 - Again!
We are all familiar with Project Euler Problem 1. This time let's try it on bigger multiples and larger range. Find the sum of ...

2 months ago

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Easy Sequences 6: Coefficient sums of derivatives
Consider the polynomial function and its first-order derivative . The sums of the coefficients of P and P', are and , respecti...

2 months ago

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Easy Sequences 11: Factorial Digits without Trailing Zeros
Here is an easy one... It is not difficult to count the number of digits of the factorial of a given number. For example for 'n...

2 months ago

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Easy Sequences 4: Eliminate the Days of Confusion
If a date is written in purely numeric format some dates can be confusing, if we don't know the date format used. For example, "...

2 months ago

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Easy Sequences 3: Prime 44-number Squares
The positive integers 62 and 238 are related. Their squares (3844 and 56,644) both end in '44'. In fact, 62 and 238 are the 3rd ...

2 months ago

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Easy Sequences 2: Trigonometric function with integral input and output
The function 'F', defined as: , will always return an integer if the input is a natural number (in radian...

2 months ago

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Easy Sequences 1: Find the index of an element
The nth element of a series is defined by: . Obviously, the first element . Given the nth element , find the value of the corre...

2 months ago

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Optimum Egyptian Fractions
Following problem was inspired by <http://www.mathworks.com/matlabcentral/cody/problems/2126-split-bread-like-the-pharaohs-egypt...

2 months ago

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Determine whether a number is practical
A number is practical if all smaller numbers can be written as a sum of the proper divisors of . The number 24 is practical bec...

3 months ago

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How many days does the cat take to climb out of the hole?
A cat accidentally falls down a hole with sloping but rough sides. It can climb out of the hole of height h metres, but for ever...

3 months ago

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Tribute to Ramanujan
The nth taxicab number, denoted as T(n), is defined as the smallest number that can be expressed as a sum of two positive algebr...

3 months ago

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Largest Geometric Series
Extension of Ned Gulley's wonderful Problem 317. In a geometric series, ratio of adjacent elements is always a constant value. ...

3 months ago

Removing duplicate rows (not "unique")
%Here's a much cleaner way to do it with 2019a or later! [B,BG]=groupcounts(A); A_reduced=BG(B==1); % or just A if you want th...

3 months ago | 0

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Leftovers? Again?!
I am thinking of a positive number X. To determine what number I am thinking of, I will give you two 1xN vectors. The first ve...

4 months ago

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Sum of all the divisors of n

4 months ago

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A <http://en.wikipedia.org/wiki/Word_ladder word ladder> transforms one word to another by means of single-letter mutations. So ...

4 months ago

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Factorions: Numbers that equal the sum of the factorials of their digits
From Wikipedia: _A factorion is a natural number that equals the sum of the factorials of its decimal digits_ For example: ...

4 months ago

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Dudeney Numbers: Numbers which are the cube of their decimal sum
From Wikipedia: _A Dudeney number is a positive integer that is a perfect cube such that the sum of its decimal digits is equa...

4 months ago