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Problem Archives

The problems archives table shows problems 1 to 1006. If you would like to tackle the 10 most recently published problems, go to Recent problems.



ID

 Title
Solved By
1Multiples of 3 or 5
849119
2Even Fibonacci Numbers
679343
3Largest Prime Factor
512573
4Largest Palindrome Product
453246
5Smallest Multiple
439735
6Sum Square Difference
444782
710 001st Prime
387608
8Largest Product in a Series
330466
9Special Pythagorean Triplet
335905
10Summation of Primes
315390
11Largest Product in a Grid
236639
12Highly Divisible Triangular Number
232965
13Large Sum
233732
14Longest Collatz Sequence
238121
15Lattice Paths
202164
16Power Digit Sum
236460
17Number Letter Counts
169695
18Maximum Path Sum I
164107
19Counting Sundays
153894
20Factorial Digit Sum
207016
21Amicable Numbers
169208
22Names Scores
155899
23Non-Abundant Sums
128753
24Lexicographic Permutations
137846
25$1000$-digit Fibonacci Number
175364
26Reciprocal Cycles
104862
27Quadratic Primes
108361
28Number Spiral Diagonals
127080
29Distinct Powers
128022
30Digit Fifth Powers
132877
31Coin Sums
104594
32Pandigital Products
89191
33Digit Cancelling Fractions
89077
34Digit Factorials
115232
35Circular Primes
103208
36Double-base Palindromes
107811
37Truncatable Primes
91171
38Pandigital Multiples
78342
39Integer Right Triangles
90127
40Champernowne's Constant
97131
41Pandigital Prime
84460
42Coded Triangle Numbers
90153
43Sub-string Divisibility
74493
44Pentagon Numbers
73025
45Triangular, Pentagonal, and Hexagonal
86547
46Goldbach's Other Conjecture
76588
47Distinct Primes Factors
72045
48Self Powers
123166
49Prime Permutations
71638
50Consecutive Prime Sum
76781