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Problem Archives

The problems archives table shows problems 1 to 1005. 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
850774
2Even Fibonacci Numbers
680518
3Largest Prime Factor
513267
4Largest Palindrome Product
453802
5Smallest Multiple
440280
6Sum Square Difference
445324
710 001st Prime
388079
8Largest Product in a Series
330788
9Special Pythagorean Triplet
336227
10Summation of Primes
315672
11Largest Product in a Grid
236765
12Highly Divisible Triangular Number
233069
13Large Sum
233858
14Longest Collatz Sequence
238253
15Lattice Paths
202241
16Power Digit Sum
236572
17Number Letter Counts
169704
18Maximum Path Sum I
164114
19Counting Sundays
153881
20Factorial Digit Sum
207042
21Amicable Numbers
169190
22Names Scores
155878
23Non-Abundant Sums
128698
24Lexicographic Permutations
137810
25$1000$-digit Fibonacci Number
175383
26Reciprocal Cycles
104827
27Quadratic Primes
108310
28Number Spiral Diagonals
127039
29Distinct Powers
127980
30Digit Fifth Powers
132811
31Coin Sums
104567
32Pandigital Products
89154
33Digit Cancelling Fractions
89033
34Digit Factorials
115185
35Circular Primes
103178
36Double-base Palindromes
107765
37Truncatable Primes
91130
38Pandigital Multiples
78310
39Integer Right Triangles
90075
40Champernowne's Constant
97101
41Pandigital Prime
84429
42Coded Triangle Numbers
90097
43Sub-string Divisibility
74454
44Pentagon Numbers
73001
45Triangular, Pentagonal, and Hexagonal
86507
46Goldbach's Other Conjecture
76562
47Distinct Primes Factors
72015
48Self Powers
123156
49Prime Permutations
71608
50Consecutive Prime Sum
76738