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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
364614
2Even Fibonacci numbers
301400
3Largest prime factor
220179
4Largest palindrome product
200531
5Smallest multiple
214069
6Sum square difference
215707
710001st prime
184759
8Largest product in a series
164086
9Special Pythagorean triplet
161932
10Summation of primes
148304
11Largest product in a grid
111635
12Highly divisible triangular number
100906
13Large sum
107491
14Longest Collatz sequence
105382
15Lattice paths
87730
16Power digit sum
110219
17Number letter counts
72512
18Maximum path sum I
71109
19Counting Sundays
65592
20Factorial digit sum
100657
21Amicable numbers
70532
22Names scores
65840
23Non-abundant sums
49511
24Lexicographic permutations
57002
251000-digit Fibonacci number
77085
26Reciprocal cycles
40593
27Quadratic primes
42818
28Number spiral diagonals
56888
29Distinct powers
51319
30Digit fifth powers
54600
31Coin sums
40336
32Pandigital products
34729
33Digit canceling fractions
35870
34Digit factorials
47658
35Circular primes
43579
36Double-base palindromes
46373
37Truncatable primes
36880
38Pandigital multiples
31309
39Integer right triangles
36242
40Champernowne's constant
40605
41Pandigital prime
33955
42Coded triangle numbers
38925
43Sub-string divisibility
28827
44Pentagon numbers
27786
45Triangular, pentagonal, and hexagonal
36916
46Goldbach's other conjecture
29567
47Distinct primes factors
28418
48Self powers
61553
49Prime permutations
28111
50Consecutive prime sum
30300