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Problems


IDDescription / TitleSolved By
1
Multiples of 3 and 5
294190
2
Even Fibonacci numbers
242549
3
Largest prime factor
176263
4
Largest palindrome product
161429
5
Smallest multiple
176325
6
Sum square difference
177893
7
10001st prime
151213
8
Largest product in a series
133606
9
Special Pythagorean triplet
133162
10
Summation of primes
121440
11
Largest product in a grid
91322
12
Highly divisible triangular number
81619
13
Large sum
88527
14
Longest Collatz sequence
86299
15
Lattice paths
71456
16
Power digit sum
92373
17
Number letter counts
59434
18
Maximum path sum I
59066
19
Counting Sundays
54065
20
Factorial digit sum
86562
21
Amicable numbers
58459
22
Names scores
54538
23
Non-abundant sums
40595
24
Lexicographic permutations
47603
25
1000-digit Fibonacci number
64677
26
Reciprocal cycles
33467
27
Quadratic primes
35384
28
Number spiral diagonals
48754
29
Distinct powers
42835
30
Digit fifth powers
45758
31
Coin sums
32939
32
Pandigital products
28621
33
Digit canceling fractions
30055
34
Digit factorials
40181
35
Circular primes
36763
36
Double-base palindromes
39509
37
Truncatable primes
30771
38
Pandigital multiples
26037
39
Integer right triangles
30282
40
Champernowne's constant
34122
41
Pandigital prime
28403
42
Coded triangle numbers
33245
43
Sub-string divisibility
23691
44
Pentagon numbers
22954
45
Triangular, pentagonal, and hexagonal
31606
46
Goldbach's other conjecture
24247
47
Distinct primes factors
23751
48
Self powers
54271
49
Prime permutations
23233
50
Consecutive prime sum
25089