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Problems


IDDescription / TitleSolved By
1
Multiples of 3 and 5
300478
2
Even Fibonacci numbers
247855
3
Largest prime factor
180294
4
Largest palindrome product
165009
5
Smallest multiple
179839
6
Sum square difference
181520
7
10001st prime
154378
8
Largest product in a series
136491
9
Special Pythagorean triplet
135876
10
Summation of primes
123934
11
Largest product in a grid
93234
12
Highly divisible triangular number
83400
13
Large sum
90312
14
Longest Collatz sequence
88116
15
Lattice paths
73007
16
Power digit sum
94138
17
Number letter counts
60673
18
Maximum path sum I
60212
19
Counting Sundays
55144
20
Factorial digit sum
88001
21
Amicable numbers
59655
22
Names scores
55637
23
Non-abundant sums
41446
24
Lexicographic permutations
48495
25
1000-digit Fibonacci number
65848
26
Reciprocal cycles
34095
27
Quadratic primes
36052
28
Number spiral diagonals
49559
29
Distinct powers
43641
30
Digit fifth powers
46586
31
Coin sums
33602
32
Pandigital products
29168
33
Digit canceling fractions
30604
34
Digit factorials
40889
35
Circular primes
37406
36
Double-base palindromes
40167
37
Truncatable primes
31345
38
Pandigital multiples
26525
39
Integer right triangles
30851
40
Champernowne's constant
34779
41
Pandigital prime
28928
42
Coded triangle numbers
33827
43
Sub-string divisibility
24174
44
Pentagon numbers
23380
45
Triangular, pentagonal, and hexagonal
32123
46
Goldbach's other conjecture
24737
47
Distinct primes factors
24189
48
Self powers
55036
49
Prime permutations
23679
50
Consecutive prime sum
25558