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Problem Archives

The problems archives table shows problems 1 to 911. If you would like to tackle the 10 most recently published problems, go to Recent problems.


ID

TitleSolved By
1Multiples of 3 or 5
1016767
2Even Fibonacci Numbers
810089
3Largest Prime Factor
583500
4Largest Palindrome Product
515732
5Smallest Multiple
518284
6Sum Square Difference
521817
7$10\,001$st Prime
446358
8Largest Product in a Series
374120
9Special Pythagorean Triplet
379291
10Summation of Primes
348250
11Largest Product in a Grid
250096
12Highly Divisible Triangular Number
236694
13Large Sum
241876
14Longest Collatz Sequence
242410
15Lattice Paths
200428
16Power Digit Sum
244613
17Number Letter Counts
162776
18Maximum Path Sum I
155880
19Counting Sundays
144730
20Factorial Digit Sum
211612
21Amicable Numbers
157169
22Names Scores
144411
23Non-Abundant Sums
112841
24Lexicographic Permutations
123557
25$1000$-digit Fibonacci Number
166668
26Reciprocal Cycles
91239
27Quadratic Primes
94697
28Number Spiral Diagonals
115920
29Distinct Powers
113793
30Digit Fifth Powers
118392
31Coin Sums
92392
32Pandigital Products
77531
33Digit Cancelling Fractions
77803
34Digit Factorials
101664
35Circular Primes
91567
36Double-base Palindromes
95707
37Truncatable Primes
79739
38Pandigital Multiples
68494
39Integer Right Triangles
79242
40Champernowne's Constant
86398
41Pandigital Prime
74031
42Coded Triangle Numbers
80299
43Sub-string Divisibility
65181
44Pentagon Numbers
63816
45Triangular, Pentagonal, and Hexagonal
76645
46Goldbach's Other Conjecture
67101
47Distinct Primes Factors
63170
48Self Powers
120007
49Prime Permutations
63007
50Consecutive Prime Sum
67979