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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
384556
2Even Fibonacci numbers
317909
3Largest prime factor
232356
4Largest palindrome product
211349
5Smallest multiple
224642
6Sum square difference
226346
710001st prime
194036
8Largest product in a series
171766
9Special Pythagorean triplet
169794
10Summation of primes
155572
11Largest product in a grid
116816
12Highly divisible triangular number
105882
13Large sum
112472
14Longest Collatz sequence
110378
15Lattice paths
91894
16Power digit sum
115296
17Number letter counts
75863
18Maximum path sum I
74257
19Counting Sundays
68517
20Factorial digit sum
104864
21Amicable numbers
73648
22Names scores
68811
23Non-abundant sums
51777
24Lexicographic permutations
59448
251000-digit Fibonacci number
80436
26Reciprocal cycles
42394
27Quadratic primes
44697
28Number spiral diagonals
59051
29Distinct powers
53681
30Digit fifth powers
56962
31Coin sums
42202
32Pandigital products
36282
33Digit canceling fractions
37426
34Digit factorials
49636
35Circular primes
45377
36Double-base palindromes
48197
37Truncatable primes
38456
38Pandigital multiples
32680
39Integer right triangles
37843
40Champernowne's constant
42336
41Pandigital prime
35380
42Coded triangle numbers
40452
43Sub-string divisibility
30178
44Pentagon numbers
29061
45Triangular, pentagonal, and hexagonal
38420
46Goldbach's other conjecture
31007
47Distinct primes factors
29654
48Self powers
63888
49Prime permutations
29426
50Consecutive prime sum
31631