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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
366321
2Even Fibonacci numbers
302714
3Largest prime factor
221142
4Largest palindrome product
201349
5Smallest multiple
214901
6Sum square difference
216539
710001st prime
185439
8Largest product in a series
164710
9Special Pythagorean triplet
162533
10Summation of primes
148855
11Largest product in a grid
112050
12Highly divisible triangular number
101286
13Large sum
107840
14Longest Collatz sequence
105765
15Lattice paths
88034
16Power digit sum
110586
17Number letter counts
72778
18Maximum path sum I
71346
19Counting Sundays
65820
20Factorial digit sum
100948
21Amicable numbers
70761
22Names scores
66059
23Non-abundant sums
49680
24Lexicographic permutations
57179
251000-digit Fibonacci number
77352
26Reciprocal cycles
40731
27Quadratic primes
42951
28Number spiral diagonals
57030
29Distinct powers
51476
30Digit fifth powers
54769
31Coin sums
40464
32Pandigital products
34847
33Digit canceling fractions
35978
34Digit factorials
47809
35Circular primes
43711
36Double-base palindromes
46497
37Truncatable primes
36981
38Pandigital multiples
31409
39Integer right triangles
36364
40Champernowne's constant
40739
41Pandigital prime
34068
42Coded triangle numbers
39046
43Sub-string divisibility
28939
44Pentagon numbers
27887
45Triangular, pentagonal, and hexagonal
37030
46Goldbach's other conjecture
29676
47Distinct primes factors
28513
48Self powers
61719
49Prime permutations
28215
50Consecutive prime sum
30385