Sum of remaining of 2^k divided by 2003
41002
sum of integers using order of integers and primitive roots
106431
Remaining volume of a sphere
81589
Find the sum of $\sum_{k=0}^{\infty} 1/[(r+2k+2)(s+2k+2)]$
139173
To find last two digits of $2^{100}$
52416
The final number after $999$ operations.
134311
How to determine equation for $\sum_{k=1}^n k^3$
132984
$\sum\limits_{k=0}^{\frac{p-1}2}3^k\binom{p}{k}\equiv 2^p-1\pmod{p^2}$
69045
Solving this summation: $\sum_{i=1}^k i\cdot2^i$
45588
Summing a series with a changing power
62463
A pencil approach to find $\sum \limits_{i=1}^{69} \sqrt{\left( 1+\frac{1}{i^2}+\frac{1}{(i+1)^2}\right)}$
137249
find $\sum_{k=2}^{\infty}\frac{1}{k^2-1}$
12760
The last 2 digits of $7^{7^{7^7}}$
17243
Remainder when $2009^{2009}-1982^{2009}-1972^{2009}+1945^{2009}$ is divided by $1998$
86163
Evaluate $\prod \frac {2k - 1} {2k}$
140008
I need help with a double sum
26614
Fermat: Last two digits of $7^{355}$
142985
Finding sum of series $\sum^{\infty}_{k=0}\frac{(k+1)(k+2)}{2^k}$