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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
364688
2Even Fibonacci numbers
301456
3Largest prime factor
220234
4Largest palindrome product
200566
5Smallest multiple
214094
6Sum square difference
215748
710001st prime
184789
8Largest product in a series
164110
9Special Pythagorean triplet
161957
10Summation of primes
148333
11Largest product in a grid
111650
12Highly divisible triangular number
100916
13Large sum
107506
14Longest Collatz sequence
105404
15Lattice paths
87738
16Power digit sum
110235
17Number letter counts
72520
18Maximum path sum I
71114
19Counting Sundays
65598
20Factorial digit sum
100668
21Amicable numbers
70540
22Names scores
65847
23Non-abundant sums
49519
24Lexicographic permutations
57009
251000-digit Fibonacci number
77095
26Reciprocal cycles
40597
27Quadratic primes
42821
28Number spiral diagonals
56894
29Distinct powers
51322
30Digit fifth powers
54608
31Coin sums
40342
32Pandigital products
34734
33Digit canceling fractions
35876
34Digit factorials
47665
35Circular primes
43580
36Double-base palindromes
46375
37Truncatable primes
36882
38Pandigital multiples
31312
39Integer right triangles
36242
40Champernowne's constant
40607
41Pandigital prime
33957
42Coded triangle numbers
38928
43Sub-string divisibility
28830
44Pentagon numbers
27788
45Triangular, pentagonal, and hexagonal
36921
46Goldbach's other conjecture
29571
47Distinct primes factors
28423
48Self powers
61563
49Prime permutations
28120
50Consecutive prime sum
30306