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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
678384
3Largest Prime Factor
512014
4Largest Palindrome Product
452780
5Smallest Multiple
439257
6Sum Square Difference
444312
710 001st Prime
387249
8Largest Product in a Series
330206
9Special Pythagorean Triplet
335641
10Summation of Primes
315180
11Largest Product in a Grid
236522
12Highly Divisible Triangular Number
232874
13Large Sum
233662
14Longest Collatz Sequence
238042
15Lattice Paths
202121
16Power Digit Sum
236406
17Number Letter Counts
169690
18Maximum Path Sum I
164101
19Counting Sundays
153906
20Factorial Digit Sum
207002
21Amicable Numbers
169215
22Names Scores
155914
23Non-Abundant Sums
128785
24Lexicographic Permutations
137887
25$1000$-digit Fibonacci Number
175387
26Reciprocal Cycles
104918
27Quadratic Primes
108402
28Number Spiral Diagonals
127133
29Distinct Powers
128060
30Digit Fifth Powers
132947
31Coin Sums
104611
32Pandigital Products
89230
33Digit Cancelling Fractions
89123
34Digit Factorials
115285
35Circular Primes
103235
36Double-base Palindromes
107877
37Truncatable Primes
91205
38Pandigital Multiples
78367
39Integer Right Triangles
90164
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
76614
47Distinct Primes Factors
72074
48Self Powers
123193
49Prime Permutations
71674
50Consecutive Prime Sum
76808