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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
385696
2Even Fibonacci numbers
318809
3Largest prime factor
232989
4Largest palindrome product
211916
5Smallest multiple
225189
6Sum square difference
226915
710001st prime
194562
8Largest product in a series
172173
9Special Pythagorean triplet
170246
10Summation of primes
155981
11Largest product in a grid
117086
12Highly divisible triangular number
106154
13Large sum
112748
14Longest Collatz sequence
110645
15Lattice paths
92111
16Power digit sum
115552
17Number letter counts
76039
18Maximum path sum I
74425
19Counting Sundays
68667
20Factorial digit sum
105050
21Amicable numbers
73824
22Names scores
68949
23Non-abundant sums
51894
24Lexicographic permutations
59565
251000-digit Fibonacci number
80585
26Reciprocal cycles
42483
27Quadratic primes
44788
28Number spiral diagonals
59152
29Distinct powers
53786
30Digit fifth powers
57080
31Coin sums
42301
32Pandigital products
36368
33Digit canceling fractions
37499
34Digit factorials
49746
35Circular primes
45466
36Double-base palindromes
48290
37Truncatable primes
38532
38Pandigital multiples
32749
39Integer right triangles
37927
40Champernowne's constant
42424
41Pandigital prime
35449
42Coded triangle numbers
40522
43Sub-string divisibility
30241
44Pentagon numbers
29127
45Triangular, pentagonal, and hexagonal
38487
46Goldbach's other conjecture
31069
47Distinct primes factors
29727
48Self powers
63984
49Prime permutations
29485
50Consecutive prime sum
31694