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Problem Archives

The problems archives table shows problems 1 to 990. 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
1035781
2Even Fibonacci Numbers
823699
3Largest Prime Factor
593026
4Largest Palindrome Product
523515
5Smallest Multiple
525808
6Sum Square Difference
529544
710 001st Prime
452540
8Largest Product in a Series
379179
9Special Pythagorean Triplet
384318
10Summation of Primes
353223
11Largest Product in a Grid
253562
12Highly Divisible Triangular Number
240231
13Large Sum
245115
14Longest Collatz Sequence
245886
15Lattice Paths
203526
16Power Digit Sum
248002
17Number Letter Counts
165323
18Maximum Path Sum I
158395
19Counting Sundays
147041
20Factorial Digit Sum
214534
21Amicable Numbers
159689
22Names Scores
146658
23Non-Abundant Sums
115133
24Lexicographic Permutations
125805
25$1000$-digit Fibonacci Number
169331
26Reciprocal Cycles
93284
27Quadratic Primes
96780
28Number Spiral Diagonals
118065
29Distinct Powers
115981
30Digit Fifth Powers
120588
31Coin Sums
94502
32Pandigital Products
79401
33Digit Cancelling Fractions
79647
34Digit Factorials
103817
35Circular Primes
93591
36Double-base Palindromes
97660
37Truncatable Primes
81658
38Pandigital Multiples
70185
39Integer Right Triangles
81057
40Champernowne's Constant
88200
41Pandigital Prime
75824
42Coded Triangle Numbers
82049
43Sub-string Divisibility
66832
44Pentagon Numbers
65505
45Triangular, Pentagonal, and Hexagonal
78459
46Goldbach's Other Conjecture
68855
47Distinct Primes Factors
64845
48Self Powers
122087
49Prime Permutations
64668
50Consecutive Prime Sum
69748