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Problems


IDDescription / TitleSolved By
1Multiples of 3 and 5
381122
2Even Fibonacci numbers
315131
3Largest prime factor
230336
4Largest palindrome product
209598
5Smallest multiple
222926
6Sum square difference
224635
710001st prime
192557
8Largest product in a series
170566
9Special Pythagorean triplet
168591
10Summation of primes
154432
11Largest product in a grid
116021
12Highly divisible triangular number
105131
13Large sum
111736
14Longest Collatz sequence
109607
15Lattice paths
91256
16Power digit sum
114567
17Number letter counts
75386
18Maximum path sum I
73773
19Counting Sundays
68092
20Factorial digit sum
104227
21Amicable numbers
73161
22Names scores
68347
23Non-abundant sums
51439
24Lexicographic permutations
59075
251000-digit Fibonacci number
79965
26Reciprocal cycles
42141
27Quadratic primes
44435
28Number spiral diagonals
58735
29Distinct powers
53350
30Digit fifth powers
56647
31Coin sums
41946
32Pandigital products
36071
33Digit canceling fractions
37217
34Digit factorials
49381
35Circular primes
45116
36Double-base palindromes
47932
37Truncatable primes
38222
38Pandigital multiples
32499
39Integer right triangles
37619
40Champernowne's constant
42124
41Pandigital prime
35192
42Coded triangle numbers
40256
43Sub-string divisibility
29977
44Pentagon numbers
28889
45Triangular, pentagonal, and hexagonal
38240
46Goldbach's other conjecture
30812
47Distinct primes factors
29482
48Self powers
63608
49Prime permutations
29243
50Consecutive prime sum
31436