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Problems


IDDescription / TitleSolved By
1
Multiples of 3 and 5
294225
2
Even Fibonacci numbers
242585
3
Largest prime factor
176284
4
Largest palindrome product
161443
5
Smallest multiple
176344
6
Sum square difference
177914
7
10001st prime
151233
8
Largest product in a series
133623
9
Special Pythagorean triplet
133173
10
Summation of primes
121454
11
Largest product in a grid
91330
12
Highly divisible triangular number
81635
13
Large sum
88538
14
Longest Collatz sequence
86314
15
Lattice paths
71465
16
Power digit sum
92382
17
Number letter counts
59438
18
Maximum path sum I
59077
19
Counting Sundays
54071
20
Factorial digit sum
86573
21
Amicable numbers
58465
22
Names scores
54550
23
Non-abundant sums
40598
24
Lexicographic permutations
47604
25
1000-digit Fibonacci number
64683
26
Reciprocal cycles
33470
27
Quadratic primes
35387
28
Number spiral diagonals
48763
29
Distinct powers
42840
30
Digit fifth powers
45764
31
Coin sums
32944
32
Pandigital products
28624
33
Digit canceling fractions
30060
34
Digit factorials
40187
35
Circular primes
36767
36
Double-base palindromes
39509
37
Truncatable primes
30774
38
Pandigital multiples
26041
39
Integer right triangles
30284
40
Champernowne's constant
34125
41
Pandigital prime
28405
42
Coded triangle numbers
33246
43
Sub-string divisibility
23693
44
Pentagon numbers
22957
45
Triangular, pentagonal, and hexagonal
31607
46
Goldbach's other conjecture
24250
47
Distinct primes factors
23755
48
Self powers
54275
49
Prime permutations
23236
50
Consecutive prime sum
25096