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Problem Archives

The problems archives table shows problems 1 to 1003. 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
853255
2Even Fibonacci Numbers
682306
3Largest Prime Factor
514334
4Largest Palindrome Product
454651
5Smallest Multiple
441148
6Sum Square Difference
446144
710 001st Prime
388774
8Largest Product in a Series
331196
9Special Pythagorean Triplet
336703
10Summation of Primes
316081
11Largest Product in a Grid
236893
12Highly Divisible Triangular Number
233206
13Large Sum
233980
14Longest Collatz Sequence
238362
15Lattice Paths
202254
16Power Digit Sum
236710
17Number Letter Counts
169694
18Maximum Path Sum I
164075
19Counting Sundays
153863
20Factorial Digit Sum
207032
21Amicable Numbers
169173
22Names Scores
155890
23Non-Abundant Sums
128617
24Lexicographic Permutations
137748
25$1000$-digit Fibonacci Number
175373
26Reciprocal Cycles
104743
27Quadratic Primes
108247
28Number Spiral Diagonals
126971
29Distinct Powers
127927
30Digit Fifth Powers
132719
31Coin Sums
104499
32Pandigital Products
89094
33Digit Cancelling Fractions
88954
34Digit Factorials
115097
35Circular Primes
103114
36Double-base Palindromes
107677
37Truncatable Primes
91062
38Pandigital Multiples
78257
39Integer Right Triangles
90002
40Champernowne's Constant
97030
41Pandigital Prime
84384
42Coded Triangle Numbers
90019
43Sub-string Divisibility
74385
44Pentagon Numbers
72944
45Triangular, Pentagonal, and Hexagonal
86420
46Goldbach's Other Conjecture
76499
47Distinct Primes Factors
71969
48Self Powers
123096
49Prime Permutations
71571
50Consecutive Prime Sum
76676