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Problems


IDDescription / TitleSolved By
1
Multiples of 3 and 5
294345
2
Even Fibonacci numbers
242686
3
Largest prime factor
176368
4
Largest palindrome product
161519
5
Smallest multiple
176422
6
Sum square difference
177991
7
10001st prime
151289
8
Largest product in a series
133688
9
Special Pythagorean triplet
133236
10
Summation of primes
121497
11
Largest product in a grid
91361
12
Highly divisible triangular number
81678
13
Large sum
88585
14
Longest Collatz sequence
86349
15
Lattice paths
71510
16
Power digit sum
92424
17
Number letter counts
59471
18
Maximum path sum I
59104
19
Counting Sundays
54089
20
Factorial digit sum
86601
21
Amicable numbers
58487
22
Names scores
54572
23
Non-abundant sums
40616
24
Lexicographic permutations
47621
25
1000-digit Fibonacci number
64709
26
Reciprocal cycles
33479
27
Quadratic primes
35400
28
Number spiral diagonals
48779
29
Distinct powers
42853
30
Digit fifth powers
45778
31
Coin sums
32954
32
Pandigital products
28636
33
Digit canceling fractions
30075
34
Digit factorials
40197
35
Circular primes
36779
36
Double-base palindromes
39518
37
Truncatable primes
30793
38
Pandigital multiples
26049
39
Integer right triangles
30298
40
Champernowne's constant
34138
41
Pandigital prime
28419
42
Coded triangle numbers
33260
43
Sub-string divisibility
23701
44
Pentagon numbers
22963
45
Triangular, pentagonal, and hexagonal
31623
46
Goldbach's other conjecture
24267
47
Distinct primes factors
23766
48
Self powers
54285
49
Prime permutations
23244
50
Consecutive prime sum
25104