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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
851546
2Even Fibonacci Numbers
681036
3Largest Prime Factor
513589
4Largest Palindrome Product
454026
5Smallest Multiple
440532
6Sum Square Difference
445554
710 001st Prime
388313
8Largest Product in a Series
330916
9Special Pythagorean Triplet
336399
10Summation of Primes
315821
11Largest Product in a Grid
236810
12Highly Divisible Triangular Number
233129
13Large Sum
233896
14Longest Collatz Sequence
238282
15Lattice Paths
202242
16Power Digit Sum
236596
17Number Letter Counts
169695
18Maximum Path Sum I
164111
19Counting Sundays
153877
20Factorial Digit Sum
207046
21Amicable Numbers
169188
22Names Scores
155864
23Non-Abundant Sums
128675
24Lexicographic Permutations
137793
25$1000$-digit Fibonacci Number
175380
26Reciprocal Cycles
104811
27Quadratic Primes
108295
28Number Spiral Diagonals
127006
29Distinct Powers
127967
30Digit Fifth Powers
132776
31Coin Sums
104541
32Pandigital Products
89143
33Digit Cancelling Fractions
89009
34Digit Factorials
115162
35Circular Primes
103162
36Double-base Palindromes
107742
37Truncatable Primes
91116
38Pandigital Multiples
78298
39Integer Right Triangles
90055
40Champernowne's Constant
97081
41Pandigital Prime
84426
42Coded Triangle Numbers
90072
43Sub-string Divisibility
74441
44Pentagon Numbers
72991
45Triangular, Pentagonal, and Hexagonal
86486
46Goldbach's Other Conjecture
76547
47Distinct Primes Factors
72011
48Self Powers
123148
49Prime Permutations
71592
50Consecutive Prime Sum
76727