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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
381102
2Even Fibonacci numbers
315114
3Largest prime factor
230327
4Largest palindrome product
209590
5Smallest multiple
222915
6Sum square difference
224626
710001st prime
192550
8Largest product in a series
170558
9Special Pythagorean triplet
168581
10Summation of primes
154425
11Largest product in a grid
116011
12Highly divisible triangular number
105118
13Large sum
111731
14Longest Collatz sequence
109599
15Lattice paths
91249
16Power digit sum
114561
17Number letter counts
75381
18Maximum path sum I
73771
19Counting Sundays
68088
20Factorial digit sum
104218
21Amicable numbers
73157
22Names scores
68342
23Non-abundant sums
51435
24Lexicographic permutations
59074
251000-digit Fibonacci number
79963
26Reciprocal cycles
42141
27Quadratic primes
44434
28Number spiral diagonals
58733
29Distinct powers
53347
30Digit fifth powers
56645
31Coin sums
41944
32Pandigital products
36067
33Digit canceling fractions
37212
34Digit factorials
49378
35Circular primes
45112
36Double-base palindromes
47930
37Truncatable primes
38217
38Pandigital multiples
32494
39Integer right triangles
37613
40Champernowne's constant
42120
41Pandigital prime
35188
42Coded triangle numbers
40252
43Sub-string divisibility
29976
44Pentagon numbers
28888
45Triangular, pentagonal, and hexagonal
38239
46Goldbach's other conjecture
30811
47Distinct primes factors
29481
48Self powers
63605
49Prime permutations
29242
50Consecutive prime sum
31435