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Problem Archives

The problems archives table shows problems 1 to 1007. 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
847826
2Even Fibonacci Numbers
678388
3Largest Prime Factor
512014
4Largest Palindrome Product
452784
5Smallest Multiple
439260
6Sum Square Difference
444318
710 001st Prime
387254
8Largest Product in a Series
330210
9Special Pythagorean Triplet
335644
10Summation of Primes
315182
11Largest Product in a Grid
236522
12Highly Divisible Triangular Number
232875
13Large Sum
233665
14Longest Collatz Sequence
238042
15Lattice Paths
202122
16Power Digit Sum
236408
17Number Letter Counts
169690
18Maximum Path Sum I
164103
19Counting Sundays
153906
20Factorial Digit Sum
207002
21Amicable Numbers
169218
22Names Scores
155916
23Non-Abundant Sums
128785
24Lexicographic Permutations
137888
25$1000$-digit Fibonacci Number
175387
26Reciprocal Cycles
104919
27Quadratic Primes
108402
28Number Spiral Diagonals
127135
29Distinct Powers
128060
30Digit Fifth Powers
132948
31Coin Sums
104611
32Pandigital Products
89231
33Digit Cancelling Fractions
89124
34Digit Factorials
115285
35Circular Primes
103235
36Double-base Palindromes
107878
37Truncatable Primes
91205
38Pandigital Multiples
78367
39Integer Right Triangles
90165
40Champernowne's Constant
97140
41Pandigital Prime
84485
42Coded Triangle Numbers
90198
43Sub-string Divisibility
74539
44Pentagon Numbers
73055
45Triangular, Pentagonal, and Hexagonal
86583
46Goldbach's Other Conjecture
76617
47Distinct Primes Factors
72074
48Self Powers
123194
49Prime Permutations
71674
50Consecutive Prime Sum
76808