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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
850028
2Even Fibonacci Numbers
679972
3Largest Prime Factor
512955
4Largest Palindrome Product
453561
5Smallest Multiple
440041
6Sum Square Difference
445101
710 001st Prime
387877
8Largest Product in a Series
330655
9Special Pythagorean Triplet
336096
10Summation of Primes
315549
11Largest Product in a Grid
236704
12Highly Divisible Triangular Number
233029
13Large Sum
233805
14Longest Collatz Sequence
238195
15Lattice Paths
202197
16Power Digit Sum
236535
17Number Letter Counts
169704
18Maximum Path Sum I
164117
19Counting Sundays
153888
20Factorial Digit Sum
207042
21Amicable Numbers
169200
22Names Scores
155883
23Non-Abundant Sums
128720
24Lexicographic Permutations
137828
25$1000$-digit Fibonacci Number
175383
26Reciprocal Cycles
104844
27Quadratic Primes
108337
28Number Spiral Diagonals
127065
29Distinct Powers
128001
30Digit Fifth Powers
132848
31Coin Sums
104582
32Pandigital Products
89171
33Digit Cancelling Fractions
89055
34Digit Factorials
115208
35Circular Primes
103188
36Double-base Palindromes
107785
37Truncatable Primes
91146
38Pandigital Multiples
78320
39Integer Right Triangles
90094
40Champernowne's Constant
97114
41Pandigital Prime
84444
42Coded Triangle Numbers
90118
43Sub-string Divisibility
74469
44Pentagon Numbers
73008
45Triangular, Pentagonal, and Hexagonal
86531
46Goldbach's Other Conjecture
76575
47Distinct Primes Factors
72027
48Self Powers
123165
49Prime Permutations
71619
50Consecutive Prime Sum
76755