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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
364120
2Even Fibonacci numbers
300958
3Largest prime factor
219878
4Largest palindrome product
200266
5Smallest multiple
213828
6Sum square difference
215456
710001st prime
184541
8Largest product in a series
163886
9Special Pythagorean triplet
161750
10Summation of primes
148134
11Largest product in a grid
111494
12Highly divisible triangular number
100778
13Large sum
107355
14Longest Collatz sequence
105262
15Lattice paths
87631
16Power digit sum
110085
17Number letter counts
72414
18Maximum path sum I
71034
19Counting Sundays
65535
20Factorial digit sum
100572
21Amicable numbers
70456
22Names scores
65780
23Non-abundant sums
49451
24Lexicographic permutations
56944
251000-digit Fibonacci number
76999
26Reciprocal cycles
40547
27Quadratic primes
42769
28Number spiral diagonals
56826
29Distinct powers
51256
30Digit fifth powers
54531
31Coin sums
40293
32Pandigital products
34685
33Digit canceling fractions
35821
34Digit factorials
47608
35Circular primes
43529
36Double-base palindromes
46326
37Truncatable primes
36835
38Pandigital multiples
31268
39Integer right triangles
36195
40Champernowne's constant
40564
41Pandigital prime
33919
42Coded triangle numbers
38886
43Sub-string divisibility
28796
44Pentagon numbers
27752
45Triangular, pentagonal, and hexagonal
36886
46Goldbach's other conjecture
29539
47Distinct primes factors
28394
48Self powers
61503
49Prime permutations
28081
50Consecutive prime sum
30260