Sum of Squares of odd numbers
20443
Calculate sum of squares of first $n$ odd numbers
147766
Sum of Permutations from 0 to n
153769
Numbers that can be expressed as the sum of two cubes in exactly two different ways
11359
Determine the Set of a Sum of Numbers
123267
Proving that even numbers equal the sum of two odd numbers.
101573
Subtracting even and odd binomial coefficients?
18932
Squares in arithmetic progression
75229
Can there be a function that's even and odd at the same time?
41789
Fermat's theorem on sums of two squares
29799
Sum of four squares not a prime
20548
General formula to obtain triangular-square numbers
114796
Direct proof that the product of odd integers is odd
91560
Square Fibonacci numbers
131883
Adding "odd" numbers
50606
Find $\sum\limits_{k\, \text{ odd}} \frac{2(k^2-1)}{k^4+k^2+1}$
140433
The number of ways of writing an integer as a sum of two squares
142303
Alternating sum of binomial coefficients multiplied by (1/k+1)