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Any nontrivial factor of M1277 = 2^1277 − 1 open

M1277 — any nontrivial factor (open) Statement. Find any nontrivial divisor of M_{1277} = 2^{1277} - 1 (385 digits). No factor is known; it is the smallest…

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Factor a 60-digit semiprime open DEMO

60-digit semiprime (solvable in minutes) Statement. Factor the 60-digit semiprime 114201804804811627633576691300951890873707992626776683593531 . Solution…

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Factor RSA-260 listed

RSA-260 (solved 2026-09-03 — demo of a live ask) Statement. Find the two prime factors of RSA-260 (260 digits, 862 bits), the largest RSA Challenge number…

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Costas array of order 33 open

Find a permutation c_0, \dots, c_{32} of \{0, \dots, 32\} (a mark in row r , column c_r ) such that all displacement vectors between marks are distinct: for…

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Ternary covering code K₃(6,1) open

Find at most 72 words of length 6 over \{0, 1, 2\} such that each of the 3^6 = 729 words is within Hamming distance 1 of a chosen word (differs from it in at…

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33 points, no convex heptagon open

Place 33 distinct points with integer coordinates in \{0, \dots, 10000\}^2 , no three on a line, such that no 7 of them are in convex position (the vertices…

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29-mark Golomb ruler open

Find 29 integers 0 = m_1 < m_2 < \dots < m_{29} \le 622 whose \binom{29}{2} = 406 pairwise differences m_j - m_i are all distinct (a Golomb ruler: no distance…

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Hadamard matrix of order 668 open

Status: solved (see Known). Kept as a template for matrix certificates. Find a 668 \times 668 matrix H with entries \pm 1 whose rows are pairwise orthogonal:…

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Three MOLS of order 10 open

Find three 10 \times 10 Latin squares S_1, S_2, S_3 on the symbols \{0, \dots, 9\} (each symbol once in every row and every column) that are pairwise…

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No-three-in-line, 71×71 grid open

Place 2N = 142 points on the 71 \times 71 grid \{0, \dots, 70\}^2 so that no three of them lie on a common line, in any direction. Submit the points as [i, j]…

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