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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
385643
2Even Fibonacci numbers
318763
3Largest prime factor
232958
4Largest palindrome product
211885
5Smallest multiple
225160
6Sum square difference
226884
710001st prime
194537
8Largest product in a series
172158
9Special Pythagorean triplet
170235
10Summation of primes
155964
11Largest product in a grid
117069
12Highly divisible triangular number
106140
13Large sum
112729
14Longest Collatz sequence
110634
15Lattice paths
92101
16Power digit sum
115541
17Number letter counts
76034
18Maximum path sum I
74420
19Counting Sundays
68663
20Factorial digit sum
105042
21Amicable numbers
73820
22Names scores
68939
23Non-abundant sums
51885
24Lexicographic permutations
59556
251000-digit Fibonacci number
80577
26Reciprocal cycles
42480
27Quadratic primes
44783
28Number spiral diagonals
59149
29Distinct powers
53777
30Digit fifth powers
57068
31Coin sums
42294
32Pandigital products
36364
33Digit canceling fractions
37499
34Digit factorials
49745
35Circular primes
45464
36Double-base palindromes
48285
37Truncatable primes
38527
38Pandigital multiples
32747
39Integer right triangles
37926
40Champernowne's constant
42423
41Pandigital prime
35447
42Coded triangle numbers
40515
43Sub-string divisibility
30240
44Pentagon numbers
29126
45Triangular, pentagonal, and hexagonal
38484
46Goldbach's other conjecture
31064
47Distinct primes factors
29726
48Self powers
63973
49Prime permutations
29483
50Consecutive prime sum
31692