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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
381736
2Even Fibonacci numbers
315648
3Largest prime factor
230742
4Largest palindrome product
209946
5Smallest multiple
223279
6Sum square difference
224954
710001st prime
192852
8Largest product in a series
170806
9Special Pythagorean triplet
168843
10Summation of primes
154666
11Largest product in a grid
116171
12Highly divisible triangular number
105274
13Large sum
111881
14Longest Collatz sequence
109766
15Lattice paths
91388
16Power digit sum
114726
17Number letter counts
75494
18Maximum path sum I
73869
19Counting Sundays
68183
20Factorial digit sum
104366
21Amicable numbers
73259
22Names scores
68432
23Non-abundant sums
51510
24Lexicographic permutations
59157
251000-digit Fibonacci number
80063
26Reciprocal cycles
42182
27Quadratic primes
44491
28Number spiral diagonals
58798
29Distinct powers
53418
30Digit fifth powers
56703
31Coin sums
41987
32Pandigital products
36115
33Digit canceling fractions
37262
34Digit factorials
49431
35Circular primes
45172
36Double-base palindromes
47983
37Truncatable primes
38265
38Pandigital multiples
32536
39Integer right triangles
37657
40Champernowne's constant
42167
41Pandigital prime
35231
42Coded triangle numbers
40298
43Sub-string divisibility
30023
44Pentagon numbers
28932
45Triangular, pentagonal, and hexagonal
38281
46Goldbach's other conjecture
30855
47Distinct primes factors
29521
48Self powers
63666
49Prime permutations
29296
50Consecutive prime sum
31486