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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
385442
2Even Fibonacci numbers
318598
3Largest prime factor
232863
4Largest palindrome product
211793
5Smallest multiple
225084
6Sum square difference
226804
710001st prime
194458
8Largest product in a series
172106
9Special Pythagorean triplet
170160
10Summation of primes
155904
11Largest product in a grid
117024
12Highly divisible triangular number
106092
13Large sum
112683
14Longest Collatz sequence
110586
15Lattice paths
92064
16Power digit sum
115497
17Number letter counts
76006
18Maximum path sum I
74384
19Counting Sundays
68636
20Factorial digit sum
105002
21Amicable numbers
73777
22Names scores
68912
23Non-abundant sums
51861
24Lexicographic permutations
59539
251000-digit Fibonacci number
80550
26Reciprocal cycles
42461
27Quadratic primes
44767
28Number spiral diagonals
59134
29Distinct powers
53755
30Digit fifth powers
57049
31Coin sums
42279
32Pandigital products
36348
33Digit canceling fractions
37486
34Digit factorials
49722
35Circular primes
45449
36Double-base palindromes
48267
37Truncatable primes
38518
38Pandigital multiples
32737
39Integer right triangles
37912
40Champernowne's constant
42404
41Pandigital prime
35432
42Coded triangle numbers
40498
43Sub-string divisibility
30231
44Pentagon numbers
29113
45Triangular, pentagonal, and hexagonal
38473
46Goldbach's other conjecture
31056
47Distinct primes factors
29708
48Self powers
63959
49Prime permutations
29478
50Consecutive prime sum
31687