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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
850418
2Even Fibonacci Numbers
680258
3Largest Prime Factor
513122
4Largest Palindrome Product
453693
5Smallest Multiple
440164
6Sum Square Difference
445228
710 001st Prime
387977
8Largest Product in a Series
330735
9Special Pythagorean Triplet
336163
10Summation of Primes
315615
11Largest Product in a Grid
236741
12Highly Divisible Triangular Number
233060
13Large Sum
233846
14Longest Collatz Sequence
238235
15Lattice Paths
202225
16Power Digit Sum
236553
17Number Letter Counts
169709
18Maximum Path Sum I
164117
19Counting Sundays
153883
20Factorial Digit Sum
207043
21Amicable Numbers
169197
22Names Scores
155884
23Non-Abundant Sums
128709
24Lexicographic Permutations
137822
25$1000$-digit Fibonacci Number
175393
26Reciprocal Cycles
104837
27Quadratic Primes
108326
28Number Spiral Diagonals
127053
29Distinct Powers
127992
30Digit Fifth Powers
132829
31Coin Sums
104575
32Pandigital Products
89164
33Digit Cancelling Fractions
89044
34Digit Factorials
115195
35Circular Primes
103184
36Double-base Palindromes
107774
37Truncatable Primes
91142
38Pandigital Multiples
78320
39Integer Right Triangles
90090
40Champernowne's Constant
97110
41Pandigital Prime
84440
42Coded Triangle Numbers
90111
43Sub-string Divisibility
74465
44Pentagon Numbers
73010
45Triangular, Pentagonal, and Hexagonal
86522
46Goldbach's Other Conjecture
76569
47Distinct Primes Factors
72023
48Self Powers
123161
49Prime Permutations
71617
50Consecutive Prime Sum
76750