MathDB
Problems
Contests
National and Regional Contests
USA Contests
Withdrawn USA Contests
Online Math Open Problems
2015 Online Math Open Problems
9
2014-2015 Spring OMO #9
2014-2015 Spring OMO #9
Source:
April 14, 2015
Online Math Open
Problem Statement
Find the sum of the decimal digits of the number
5
∑
k
=
1
99
k
(
k
+
1
)
(
k
2
+
k
+
1
)
.
5\sum_{k=1}^{99} k(k + 1)(k^2 + k + 1).
5
k
=
1
∑
99
k
(
k
+
1
)
(
k
2
+
k
+
1
)
.
Proposed by Robin Park
Back to Problems
View on AoPS