Problems
1
2
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ID
8
9
10
Go to Problem: Description / Title
Solved By
1
Multiples of 3 and 5
405420
2
Even Fibonacci numbers
334075
3
Largest prime factor
243562
4
Largest palindrome product
221071
5
Smallest multiple
234248
6
Sum square difference
236024
7
10001st prime
202344
8
Largest product in a series
177967
9
Special Pythagorean triplet
176441
10
Summation of primes
161777
11
Largest product in a grid
121062
12
Highly divisible triangular number
109978
13
Large sum
116560
14
Longest Collatz sequence
114530
15
Lattice paths
95427
16
Power digit sum
119357
17
Number letter counts
78653
18
Maximum path sum I
76849
19
Counting Sundays
70998
20
Factorial digit sum
108198
21
Amicable numbers
76204
22
Names scores
71176
23
Non-‐abundant sums
53659
24
Lexicographic permutations
61403
25
1000-‐digit Fibonacci number
83181
26
Reciprocal cycles
43886
27
Quadratic primes
46219
28
Number spiral diagonals
60842
29
Distinct powers
55517
30
Digit fifth powers
58847
31
Coin sums
43752
32
Pandigital products
37522
33
Digit cancelling fractions
38643
34
Digit factorials
51240
35
Circular primes
46761
36
Double-‐base palindromes
49658
37
Truncatable primes
39709
38
Pandigital multiples
33740
39
Integer right triangles
39130
40
Champernowne's constant
43734
41
Pandigital prime
36551
42
Coded triangle numbers
41710
43
Sub-‐string divisibility
31262
44
Pentagon numbers
30089
45
Triangular, pentagonal, and hexagonal
39573
46
Goldbach's other conjecture
32066
47
Distinct primes factors
30662
48
Self powers
65705
1
49
Prime permutations
30426
50
Consecutive prime sum
32756
2
3
4
5
6
7
8
9
10
Go to Problem: Problems
1
2
3
4
5
6
7
ID
8
9
10
Go to Problem: Description / Title
Solved By
51
Prime digit replacements
16918
52
Permuted multiples
36752
53
Combinatoric selections
33372
54
Poker hands
18592
55
Lychrel numbers
30075
56
Powerful digit sum
32452
57
Square root convergents
22160
58
Spiral primes
21530
59
XOR decryption
23124
60
Prime pair sets
13432
61
Cyclical figurate numbers
13403
62
Cubic permutations
16541
63
Powerful digit counts
23555
64
Odd period square roots
11772
65
Convergents of e
16447
66
Diophantine equation
10410
67
Maximum path sum II
54653
68
Magic 5-‐gon ring
11037
69
Totient maximum
18795
70
Totient permutation
12243
71
Ordered fractions
15749
72
Counting fractions
12167
73
Counting fractions in a range
14289
74
Digit factorial chains
14661
75
Singular integer right triangles
9611
76
Counting summations
15818
77
Prime summations
10126
78
Coin partitions
8846
79
Passcode derivation
25833
80
Square root digital expansion
10855
81
Path sum: two ways
19372
82
Path sum: three ways
11675
83
Path sum: four ways
9897
84
Monopoly odds
6649
85
Counting rectangles
13753
86
Cuboid route
6786
87
Prime power triples
11432
88
Product-‐sum numbers
5028
89
Roman numerals
12241
90
Cube digit pairs
5819
91
Right triangles with integer coordinates
8484
92
Square digit chains
23391
93
Arithmetic expressions
6135
94
Almost equilateral triangles
6384
95
Amicable chains
7579
96
Su Doku
9163
97
Large non-‐Mersenne prime
27053
98
Anagramic squares
5854
99
17077
Largest exponential
100 Arranged probability
1
2
3
4
5
6
7
8599
8
9
10
Go to Problem: Problems
1
2
3
4
5
6
7
ID
8
9
10
Go to Problem: Description / Title
Solved By
101 Optimum polynomial
5870
102 Triangle containment
12182
103 Special subset sums: optimum
4255
104 Pandigital Fibonacci ends
9306
105 Special subset sums: testing
4309
106 Special subset sums: meta-‐testing
3424
107 Minimal network
6145
108 Diophantine reciprocals I
7514
109 Darts
4418
110 Diophantine reciprocals II
4709
111 Primes with runs
4015
112 Bouncy numbers
13895
113 Non-‐bouncy numbers
6487
114 Counting block combinations I
6094
115 Counting block combinations II
5591
116 Red, green or blue tiles
6758
117 Red, green, and blue tiles
6212
118 Pandigital prime sets
3682
119 Digit power sum
6899
120 Square remainders
8038
121 Disc game prize fund
5448
122 Efficient exponentiation
4289
123 Prime square remainders
6791
124 Ordered radicals
8303
125 Palindromic sums
7888
126 Cuboid layers
2446
127 abc-‐hits
3328
128 Hexagonal tile differences
2661
129 Repunit divisibility
3526
130 Composites with prime repunit property
3312
131 Prime cube partnership
4188
132 Large repunit factors
3633
133 Repunit nonfactors
3089
134 Prime pair connection
3987
135 Same differences
3545
136 Singleton difference
3136
137 Fibonacci golden nuggets
3010
138 Special isosceles triangles
3306
139 Pythagorean tiles
3098
140 Modified Fibonacci golden nuggets
2351
141 Investigating progressive numbers, n, which are also square
2051
142 Perfect Square Collection
3325
143 Investigating the Torricelli point of a triangle
1436
144 Investigating multiple reflections of a laser beam
3312
145 How many reversible numbers are there below one-‐billion?
9294
146 Investigating a Prime Pattern
2799
147 Rectangles in cross-‐hatched grids
1578
148 Exploring Pascal's triangle
2927
149 Searching for a maximum-‐sum subsequence
150
1
2
Searching a triangular array for a sub-‐triangle having
minimum-‐sum
3
4
5
6
7
8
9
10
Go to Problem: 2717
2171