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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
364943
2Even Fibonacci numbers
301671
3Largest prime factor
220404
4Largest palindrome product
200725
5Smallest multiple
214262
6Sum square difference
215902
710001st prime
184927
8Largest product in a series
164222
9Special Pythagorean triplet
162069
10Summation of primes
148440
11Largest product in a grid
111736
12Highly divisible triangular number
101007
13Large sum
107578
14Longest Collatz sequence
105480
15Lattice paths
87795
16Power digit sum
110301
17Number letter counts
72576
18Maximum path sum I
71162
19Counting Sundays
65644
20Factorial digit sum
100732
21Amicable numbers
70594
22Names scores
65899
23Non-abundant sums
49553
24Lexicographic permutations
57047
251000-digit Fibonacci number
77138
26Reciprocal cycles
40624
27Quadratic primes
42849
28Number spiral diagonals
56917
29Distinct powers
51356
30Digit fifth powers
54633
31Coin sums
40367
32Pandigital products
34754
33Digit canceling fractions
35895
34Digit factorials
47696
35Circular primes
43604
36Double-base palindromes
46399
37Truncatable primes
36905
38Pandigital multiples
31334
39Integer right triangles
36263
40Champernowne's constant
40636
41Pandigital prime
33980
42Coded triangle numbers
38947
43Sub-string divisibility
28846
44Pentagon numbers
27810
45Triangular, pentagonal, and hexagonal
36941
46Goldbach's other conjecture
29587
47Distinct primes factors
28437
48Self powers
61588
49Prime permutations
28139
50Consecutive prime sum
30320