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Problem Archives

The problems archives table shows problems 1 to 1004. 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
852650
2Even Fibonacci Numbers
681834
3Largest Prime Factor
514061
4Largest Palindrome Product
454422
5Smallest Multiple
440937
6Sum Square Difference
445929
710 001st Prime
388599
8Largest Product in a Series
331088
9Special Pythagorean Triplet
336591
10Summation of Primes
315977
11Largest Product in a Grid
236850
12Highly Divisible Triangular Number
233163
13Large Sum
233949
14Longest Collatz Sequence
238317
15Lattice Paths
202245
16Power Digit Sum
236664
17Number Letter Counts
169686
18Maximum Path Sum I
164074
19Counting Sundays
153864
20Factorial Digit Sum
207023
21Amicable Numbers
169181
22Names Scores
155886
23Non-Abundant Sums
128632
24Lexicographic Permutations
137756
25$1000$-digit Fibonacci Number
175370
26Reciprocal Cycles
104764
27Quadratic Primes
108263
28Number Spiral Diagonals
126977
29Distinct Powers
127946
30Digit Fifth Powers
132729
31Coin Sums
104513
32Pandigital Products
89110
33Digit Cancelling Fractions
88973
34Digit Factorials
115114
35Circular Primes
103124
36Double-base Palindromes
107693
37Truncatable Primes
91077
38Pandigital Multiples
78271
39Integer Right Triangles
90025
40Champernowne's Constant
97042
41Pandigital Prime
84401
42Coded Triangle Numbers
90034
43Sub-string Divisibility
74405
44Pentagon Numbers
72957
45Triangular, Pentagonal, and Hexagonal
86440
46Goldbach's Other Conjecture
76507
47Distinct Primes Factors
71981
48Self Powers
123108
49Prime Permutations
71579
50Consecutive Prime Sum
76686